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	$107.70	4.818%	$112.889	$112.89	$112.90	$112.90
Purchase #2	$195.74	6.533%	$208.5277	$208.53	$208.55	$208.50
Purchase #3	$238.44	4.729%	$249.7158	$249.72	$249.70	$249.70
Purchase #4	$195.78	8.455%	$212.3332	$212.33	$212.35	$212.30
Purchase #5	$32.94	13.661%	$37.4399	$37.44	$37.45	$37.40
Purchase #6	$24.72	3.851%	$25.672	$25.67	$25.65	$25.70
Purchase #7	$99.83	11.740%	$111.55	$111.55	$111.55	$111.60
7 purchase totals =	$895.15		$958.1276	$958.13	$958.15	$958.10