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	$76.49	11.574%	$85.343	$85.34	$85.35	$85.30
Purchase #2	$80.30	12.605%	$90.4218	$90.42	$90.40	$90.40
Purchase #3	$105.89	9.434%	$115.8797	$115.88	$115.90	$115.90
Purchase #4	$171.69	6.535%	$182.9099	$182.91	$182.90	$182.90
Purchase #5	$51.58	5.556%	$54.4458	$54.45	$54.45	$54.40
Purchase #6	$173.37	5.468%	$182.8499	$182.85	$182.85	$182.80
Purchase #7	$32.51	11.308%	$36.1862	$36.19	$36.20	$36.20
7 purchase totals =	$691.83		$748.0363	$748.04	$748.05	$747.90