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	$168.74	13.389%	$191.3326	$191.33	$191.35	$191.30
Purchase #2	$189.44	7.197%	$203.074	$203.07	$203.05	$203.10
Purchase #3	$36.47	12.561%	$41.051	$41.05	$41.05	$41.10
Purchase #4	$60.83	10.333%	$67.1156	$67.12	$67.10	$67.10
Purchase #5	$233.52	9.561%	$255.8468	$255.85	$255.85	$255.80
Purchase #6	$70.44	13.769%	$80.1389	$80.14	$80.15	$80.10
Purchase #7	$33.42	3.140%	$34.4694	$34.47	$34.45	$34.50
7 purchase totals =	$792.86		$873.0283	$873.03	$873.00	$873.00