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	$142.99	9.361%	$156.3753	$156.38	$156.40	$156.40
Purchase #2	$66.67	7.603%	$71.7389	$71.74	$71.75	$71.70
Purchase #3	$158.94	4.700%	$166.4102	$166.41	$166.40	$166.40
Purchase #4	$216.76	12.635%	$244.1476	$244.15	$244.15	$244.10
Purchase #5	$178.34	10.513%	$197.0889	$197.09	$197.10	$197.10
Purchase #6	$89.67	12.205%	$100.6142	$100.61	$100.60	$100.60
Purchase #7	$50.94	9.741%	$55.9021	$55.90	$55.90	$55.90
7 purchase totals =	$904.31		$992.2772	$992.28	$992.30	$992.20