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	$63.35	3.544%	$65.5951	$65.60	$65.60	$65.60
Purchase #2	$124.53	4.643%	$130.3119	$130.31	$130.30	$130.30
Purchase #3	$244.87	5.418%	$258.1371	$258.14	$258.15	$258.10
Purchase #4	$210.50	13.230%	$238.3492	$238.35	$238.35	$238.30
Purchase #5	$148.89	6.427%	$158.4592	$158.46	$158.45	$158.50
Purchase #6	$89.62	6.157%	$95.1379	$95.14	$95.15	$95.10
Purchase #7	$129.79	11.509%	$144.7275	$144.73	$144.75	$144.70
7 purchase totals =	$1,011.55		$1,090.7179	$1,090.73	$1,090.75	$1,090.60