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	$203.63	8.120%	$220.1648	$220.16	$220.15	$220.20
Purchase #2	$220.42	4.319%	$229.9399	$229.94	$229.95	$229.90
Purchase #3	$57.77	3.218%	$59.629	$59.63	$59.65	$59.60
Purchase #4	$85.90	7.307%	$92.1767	$92.18	$92.20	$92.20
Purchase #5	$119.57	9.117%	$130.4712	$130.47	$130.45	$130.50
Purchase #6	$82.34	8.375%	$89.236	$89.24	$89.25	$89.20
Purchase #7	$213.44	9.179%	$233.0317	$233.03	$233.05	$233.00
7 purchase totals =	$983.07		$1,054.6493	$1,054.65	$1,054.70	$1,054.60