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	$111.86	11.152%	$124.3346	$124.33	$124.35	$124.30
Purchase #2	$99.51	11.156%	$110.6113	$110.61	$110.60	$110.60
Purchase #3	$26.72	8.582%	$29.0131	$29.01	$29.00	$29.00
Purchase #4	$95.92	9.173%	$104.7187	$104.72	$104.70	$104.70
Purchase #5	$236.45	7.812%	$254.9215	$254.92	$254.90	$254.90
Purchase #6	$214.48	10.740%	$237.5152	$237.52	$237.50	$237.50
Purchase #7	$158.39	10.139%	$174.4492	$174.45	$174.45	$174.40
7 purchase totals =	$943.33		$1,035.5636	$1,035.56	$1,035.50	$1,035.40