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	$198.25	11.178%	$220.4104	$220.41	$220.40	$220.40
Purchase #2	$16.83	11.215%	$18.7175	$18.72	$18.70	$18.70
Purchase #3	$78.76	13.750%	$89.5895	$89.59	$89.60	$89.60
Purchase #4	$144.53	11.309%	$160.8749	$160.87	$160.85	$160.90
Purchase #5	$192.55	9.117%	$210.1048	$210.10	$210.10	$210.10
Purchase #6	$169.64	6.475%	$180.6242	$180.62	$180.60	$180.60
Purchase #7	$198.50	10.410%	$219.1639	$219.16	$219.15	$219.20
7 purchase totals =	$999.06		$1,099.4852	$1,099.47	$1,099.40	$1,099.50