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	$206.58	4.123%	$215.0973	$215.10	$215.10	$215.10
Purchase #2	$56.30	4.594%	$58.8864	$58.89	$58.90	$58.90
Purchase #3	$222.77	11.805%	$249.068	$249.07	$249.05	$249.10
Purchase #4	$70.27	5.465%	$74.1103	$74.11	$74.10	$74.10
Purchase #5	$192.74	13.833%	$219.4017	$219.40	$219.40	$219.40
Purchase #6	$81.53	9.301%	$89.1131	$89.11	$89.10	$89.10
Purchase #7	$152.63	4.724%	$159.8402	$159.84	$159.85	$159.80
7 purchase totals =	$982.82		$1,065.5170	$1,065.52	$1,065.50	$1,065.50