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	$98.67	12.373%	$110.8784	$110.88	$110.90	$110.90
Purchase #2	$60.93	10.837%	$67.533	$67.53	$67.55	$67.50
Purchase #3	$116.52	9.454%	$127.5358	$127.54	$127.55	$127.50
Purchase #4	$196.59	7.198%	$210.7405	$210.74	$210.75	$210.70
Purchase #5	$59.73	9.392%	$65.3398	$65.34	$65.35	$65.30
Purchase #6	$193.76	7.601%	$208.4877	$208.49	$208.50	$208.50
Purchase #7	$71.86	4.164%	$74.8523	$74.85	$74.85	$74.90
7 purchase totals =	$798.06		$865.3675	$865.37	$865.45	$865.30