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	$62.39	12.460%	$70.1638	$70.16	$70.15	$70.20
Purchase #2	$96.82	3.817%	$100.5156	$100.52	$100.50	$100.50
Purchase #3	$122.35	6.634%	$130.4667	$130.47	$130.45	$130.50
Purchase #4	$125.78	11.315%	$140.012	$140.01	$140.00	$140.00
Purchase #5	$166.79	13.845%	$189.8821	$189.88	$189.90	$189.90
Purchase #6	$190.52	11.141%	$211.7458	$211.75	$211.75	$211.70
Purchase #7	$229.54	6.343%	$244.0997	$244.10	$244.10	$244.10
7 purchase totals =	$994.19		$1,086.8857	$1,086.89	$1,086.85	$1,086.90