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	$102.66	8.344%	$111.226	$111.23	$111.25	$111.20
Purchase #2	$112.60	10.254%	$124.146	$124.15	$124.15	$124.10
Purchase #3	$7.49	13.392%	$8.4931	$8.49	$8.50	$8.50
Purchase #4	$57.90	9.290%	$63.2789	$63.28	$63.30	$63.30
Purchase #5	$72.82	13.375%	$82.5597	$82.56	$82.55	$82.60
Purchase #6	$94.89	11.781%	$106.069	$106.07	$106.05	$106.10
Purchase #7	$65.31	9.582%	$71.568	$71.57	$71.55	$71.60
7 purchase totals =	$513.67		$567.3407	$567.35	$567.35	$567.40