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	$133.27	11.444%	$148.5214	$148.52	$148.50	$148.50
Purchase #2	$95.85	3.693%	$99.3897	$99.39	$99.40	$99.40
Purchase #3	$249.99	7.694%	$269.2242	$269.22	$269.20	$269.20
Purchase #4	$28.53	12.542%	$32.1082	$32.11	$32.10	$32.10
Purchase #5	$130.74	13.321%	$148.1559	$148.16	$148.15	$148.20
Purchase #6	$190.61	4.724%	$199.6144	$199.61	$199.60	$199.60
Purchase #7	$209.66	4.711%	$219.5371	$219.54	$219.55	$219.50
7 purchase totals =	$1,038.65		$1,116.5509	$1,116.55	$1,116.50	$1,116.50