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	$56.91	10.419%	$62.8395	$62.84	$62.85	$62.80
Purchase #2	$77.34	10.558%	$85.5056	$85.51	$85.50	$85.50
Purchase #3	$230.71	4.773%	$241.7218	$241.72	$241.70	$241.70
Purchase #4	$196.81	3.496%	$203.6905	$203.69	$203.70	$203.70
Purchase #5	$223.98	3.279%	$231.3243	$231.32	$231.30	$231.30
Purchase #6	$128.93	8.161%	$139.452	$139.45	$139.45	$139.50
Purchase #7	$29.86	9.831%	$32.7955	$32.80	$32.80	$32.80
7 purchase totals =	$944.54		$997.3292	$997.33	$997.30	$997.30