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	$110.55	7.644%	$119.0004	$119.00	$119.00	$119.00
Purchase #2	$178.42	11.762%	$199.4058	$199.41	$199.40	$199.40
Purchase #3	$50.79	6.795%	$54.2412	$54.24	$54.25	$54.20
Purchase #4	$22.69	6.545%	$24.1751	$24.18	$24.20	$24.20
Purchase #5	$88.89	13.419%	$100.8181	$100.82	$100.80	$100.80
Purchase #6	$126.86	3.222%	$130.9474	$130.95	$130.95	$130.90
Purchase #7	$185.93	5.388%	$195.9479	$195.95	$195.95	$195.90
7 purchase totals =	$764.13		$824.5359	$824.55	$824.55	$824.40