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	$215.77	8.222%	$233.5106	$233.51	$233.50	$233.50
Purchase #2	$112.31	5.664%	$118.6712	$118.67	$118.65	$118.70
Purchase #3	$243.88	10.771%	$270.1483	$270.15	$270.15	$270.10
Purchase #4	$131.71	9.612%	$144.37	$144.37	$144.35	$144.40
Purchase #5	$39.79	8.801%	$43.2919	$43.29	$43.30	$43.30
Purchase #6	$21.80	5.254%	$22.9454	$22.95	$22.95	$22.90
Purchase #7	$160.94	5.112%	$169.1673	$169.17	$169.15	$169.20
7 purchase totals =	$926.20		$1,002.1047	$1,002.11	$1,002.05	$1,002.10