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	$58.54	4.453%	$61.1468	$61.15	$61.15	$61.10
Purchase #2	$47.44	10.827%	$52.5763	$52.58	$52.60	$52.60
Purchase #3	$236.68	13.737%	$269.1927	$269.19	$269.20	$269.20
Purchase #4	$144.83	5.338%	$152.561	$152.56	$152.55	$152.60
Purchase #5	$165.27	7.681%	$177.9644	$177.96	$177.95	$178.00
Purchase #6	$175.62	9.112%	$191.6225	$191.62	$191.60	$191.60
Purchase #7	$197.34	12.816%	$222.6311	$222.63	$222.65	$222.60
7 purchase totals =	$1,025.72		$1,127.6948	$1,127.69	$1,127.70	$1,127.70