Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$156.53	5.439%	$165.0437	$165.04	$165.05	$165.00
Purchase #2	$168.45	10.498%	$186.1339	$186.13	$186.15	$186.10
Purchase #3	$226.42	3.770%	$234.956	$234.96	$234.95	$235.00
Purchase #4	$140.47	7.866%	$151.5194	$151.52	$151.50	$151.50
Purchase #5	$195.82	7.524%	$210.5535	$210.55	$210.55	$210.60
Purchase #6	$120.42	11.352%	$134.0901	$134.09	$134.10	$134.10
Purchase #7	$151.32	13.762%	$172.1447	$172.14	$172.15	$172.10
7 purchase totals =	$1,159.43		$1,254.4413	$1,254.43	$1,254.45	$1,254.40