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	$160.27	3.464%	$165.8218	$165.82	$165.80	$165.80
Purchase #2	$127.40	3.400%	$131.7316	$131.73	$131.75	$131.70
Purchase #3	$50.85	8.566%	$55.2058	$55.21	$55.20	$55.20
Purchase #4	$193.54	3.650%	$200.6042	$200.60	$200.60	$200.60
Purchase #5	$65.83	11.594%	$73.4623	$73.46	$73.45	$73.50
Purchase #6	$102.41	4.126%	$106.6354	$106.64	$106.65	$106.60
Purchase #7	$196.78	7.310%	$211.1646	$211.16	$211.15	$211.20
7 purchase totals =	$897.08		$944.6257	$944.62	$944.60	$944.60