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	$156.84	4.710%	$164.2272	$164.23	$164.25	$164.20
Purchase #2	$54.93	12.164%	$61.6117	$61.61	$61.60	$61.60
Purchase #3	$246.35	12.420%	$276.9467	$276.95	$276.95	$276.90
Purchase #4	$198.54	12.731%	$223.8161	$223.82	$223.80	$223.80
Purchase #5	$246.72	11.138%	$274.1997	$274.20	$274.20	$274.20
Purchase #6	$35.75	10.825%	$39.6199	$39.62	$39.60	$39.60
Purchase #7	$168.33	12.198%	$188.8629	$188.86	$188.85	$188.90
7 purchase totals =	$1,107.46		$1,229.2842	$1,229.29	$1,229.25	$1,229.20