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	$35.29	5.262%	$37.147	$37.15	$37.15	$37.10
Purchase #2	$86.80	11.133%	$96.4634	$96.46	$96.45	$96.50
Purchase #3	$85.63	8.356%	$92.7852	$92.79	$92.80	$92.80
Purchase #4	$103.99	6.266%	$110.506	$110.51	$110.50	$110.50
Purchase #5	$65.58	9.184%	$71.6029	$71.60	$71.60	$71.60
Purchase #6	$97.25	10.761%	$107.7151	$107.72	$107.70	$107.70
Purchase #7	$60.89	10.501%	$67.2841	$67.28	$67.30	$67.30
7 purchase totals =	$535.43		$583.5037	$583.51	$583.50	$583.50