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	$78.43	11.733%	$87.6322	$87.63	$87.65	$87.60
Purchase #2	$193.25	5.104%	$203.1135	$203.11	$203.10	$203.10
Purchase #3	$166.63	4.734%	$174.5183	$174.52	$174.50	$174.50
Purchase #4	$119.83	4.126%	$124.7742	$124.77	$124.75	$124.80
Purchase #5	$120.83	6.508%	$128.6936	$128.69	$128.70	$128.70
Purchase #6	$37.82	13.473%	$42.9155	$42.92	$42.90	$42.90
Purchase #7	$108.76	13.618%	$123.5709	$123.57	$123.55	$123.60
7 purchase totals =	$825.55		$885.2182	$885.21	$885.15	$885.20