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	$216.94	11.813%	$242.5671	$242.57	$242.55	$242.60
Purchase #2	$180.78	8.659%	$196.4337	$196.43	$196.45	$196.40
Purchase #3	$135.77	4.379%	$141.7154	$141.72	$141.70	$141.70
Purchase #4	$147.75	11.780%	$165.155	$165.16	$165.15	$165.20
Purchase #5	$50.85	13.557%	$57.7437	$57.74	$57.75	$57.70
Purchase #6	$107.38	3.804%	$111.4647	$111.46	$111.45	$111.50
Purchase #7	$45.45	12.312%	$51.0458	$51.05	$51.05	$51.00
7 purchase totals =	$884.92		$966.1254	$966.13	$966.10	$966.10