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	$174.82	9.425%	$191.2968	$191.30	$191.30	$191.30
Purchase #2	$108.94	9.164%	$118.9233	$118.92	$118.90	$118.90
Purchase #3	$40.34	12.737%	$45.4781	$45.48	$45.50	$45.50
Purchase #4	$57.72	4.862%	$60.5263	$60.53	$60.55	$60.50
Purchase #5	$244.92	10.455%	$270.5264	$270.53	$270.55	$270.50
Purchase #6	$111.33	10.437%	$122.9495	$122.95	$122.95	$122.90
Purchase #7	$148.56	12.158%	$166.6219	$166.62	$166.60	$166.60
7 purchase totals =	$886.63		$976.3223	$976.33	$976.35	$976.20