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	$185.51	11.356%	$206.5765	$206.58	$206.60	$206.60
Purchase #2	$6.82	10.541%	$7.5389	$7.54	$7.55	$7.50
Purchase #3	$92.78	11.184%	$103.1565	$103.16	$103.15	$103.20
Purchase #4	$214.86	13.387%	$243.6233	$243.62	$243.60	$243.60
Purchase #5	$130.92	13.158%	$148.1465	$148.15	$148.15	$148.10
Purchase #6	$225.77	11.521%	$251.781	$251.78	$251.80	$251.80
Purchase #7	$125.91	4.496%	$131.5709	$131.57	$131.55	$131.60
7 purchase totals =	$982.57		$1,092.3936	$1,092.40	$1,092.40	$1,092.40