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	$197.98	9.776%	$217.3345	$217.33	$217.35	$217.30
Purchase #2	$172.82	4.333%	$180.3083	$180.31	$180.30	$180.30
Purchase #3	$191.97	13.264%	$217.4329	$217.43	$217.45	$217.40
Purchase #4	$200.33	9.392%	$219.145	$219.15	$219.15	$219.10
Purchase #5	$110.74	5.593%	$116.9337	$116.93	$116.95	$116.90
Purchase #6	$65.89	7.155%	$70.6044	$70.60	$70.60	$70.60
Purchase #7	$128.51	11.634%	$143.4609	$143.46	$143.45	$143.50
7 purchase totals =	$1,068.24		$1,165.2197	$1,165.21	$1,165.25	$1,165.10