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	$242.67	8.279%	$262.7606	$262.76	$262.75	$262.80
Purchase #2	$35.57	10.307%	$39.2362	$39.24	$39.25	$39.20
Purchase #3	$235.54	12.560%	$265.1238	$265.12	$265.10	$265.10
Purchase #4	$49.77	9.393%	$54.4449	$54.44	$54.45	$54.40
Purchase #5	$245.77	4.455%	$256.7191	$256.72	$256.70	$256.70
Purchase #6	$179.62	5.422%	$189.359	$189.36	$189.35	$189.40
Purchase #7	$106.61	4.651%	$111.5684	$111.57	$111.55	$111.60
7 purchase totals =	$1,095.55		$1,179.2120	$1,179.21	$1,179.15	$1,179.20