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	$69.73	12.484%	$78.4351	$78.44	$78.45	$78.40
Purchase #2	$12.52	9.650%	$13.7282	$13.73	$13.75	$13.70
Purchase #3	$28.34	11.308%	$31.5447	$31.54	$31.55	$31.50
Purchase #4	$140.54	4.118%	$146.3274	$146.33	$146.35	$146.30
Purchase #5	$178.64	8.576%	$193.9602	$193.96	$193.95	$194.00
Purchase #6	$65.77	9.300%	$71.8866	$71.89	$71.90	$71.90
Purchase #7	$229.96	9.540%	$251.8982	$251.90	$251.90	$251.90
7 purchase totals =	$725.50		$787.7804	$787.79	$787.85	$787.70