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	$105.63	6.518%	$112.515	$112.52	$112.50	$112.50
Purchase #2	$200.43	4.634%	$209.7179	$209.72	$209.70	$209.70
Purchase #3	$214.83	12.425%	$241.5226	$241.52	$241.50	$241.50
Purchase #4	$65.44	6.749%	$69.8565	$69.86	$69.85	$69.90
Purchase #5	$140.42	12.612%	$158.1298	$158.13	$158.15	$158.10
Purchase #6	$79.34	4.484%	$82.8976	$82.90	$82.90	$82.90
Purchase #7	$57.42	9.113%	$62.6527	$62.65	$62.65	$62.70
7 purchase totals =	$863.51		$937.2921	$937.30	$937.25	$937.30