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	$88.62	3.164%	$91.4239	$91.42	$91.40	$91.40
Purchase #2	$61.30	11.255%	$68.1993	$68.20	$68.20	$68.20
Purchase #3	$76.36	11.478%	$85.1246	$85.12	$85.10	$85.10
Purchase #4	$54.39	9.265%	$59.4292	$59.43	$59.45	$59.40
Purchase #5	$144.72	5.503%	$152.6839	$152.68	$152.70	$152.70
Purchase #6	$81.77	4.525%	$85.4701	$85.47	$85.45	$85.50
Purchase #7	$195.35	8.439%	$211.8356	$211.84	$211.85	$211.80
7 purchase totals =	$702.51		$754.1666	$754.16	$754.15	$754.10