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	$193.69	6.629%	$206.5297	$206.53	$206.55	$206.50
Purchase #2	$104.42	6.820%	$111.5414	$111.54	$111.55	$111.50
Purchase #3	$241.49	5.114%	$253.8398	$253.84	$253.85	$253.80
Purchase #4	$249.84	11.317%	$278.1144	$278.11	$278.10	$278.10
Purchase #5	$235.80	8.175%	$255.0767	$255.08	$255.10	$255.10
Purchase #6	$36.96	12.391%	$41.5397	$41.54	$41.55	$41.50
Purchase #7	$166.34	6.114%	$176.51	$176.51	$176.50	$176.50
7 purchase totals =	$1,228.54		$1,323.1517	$1,323.15	$1,323.20	$1,323.00