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	$176.90	13.184%	$200.2225	$200.22	$200.20	$200.20
Purchase #2	$211.80	8.190%	$229.1464	$229.15	$229.15	$229.10
Purchase #3	$246.93	11.735%	$275.9072	$275.91	$275.90	$275.90
Purchase #4	$196.59	3.367%	$203.2092	$203.21	$203.20	$203.20
Purchase #5	$79.89	3.278%	$82.5088	$82.51	$82.50	$82.50
Purchase #6	$133.45	12.295%	$149.8577	$149.86	$149.85	$149.90
Purchase #7	$19.32	5.145%	$20.314	$20.31	$20.30	$20.30
7 purchase totals =	$1,064.88		$1,161.1658	$1,161.17	$1,161.10	$1,161.10