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	$140.34	8.643%	$152.4696	$152.47	$152.45	$152.50
Purchase #2	$158.44	8.661%	$172.1625	$172.16	$172.15	$172.20
Purchase #3	$233.62	11.842%	$261.2853	$261.29	$261.30	$261.30
Purchase #4	$172.45	9.830%	$189.4018	$189.40	$189.40	$189.40
Purchase #5	$170.51	12.235%	$191.3719	$191.37	$191.35	$191.40
Purchase #6	$167.92	13.594%	$190.747	$190.75	$190.75	$190.70
Purchase #7	$156.90	6.737%	$167.4704	$167.47	$167.45	$167.50
7 purchase totals =	$1,200.18		$1,324.9085	$1,324.91	$1,324.85	$1,325.00