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	$235.67	8.314%	$255.2636	$255.26	$255.25	$255.30
Purchase #2	$83.60	7.873%	$90.1818	$90.18	$90.20	$90.20
Purchase #3	$54.73	13.254%	$61.9839	$61.98	$62.00	$62.00
Purchase #4	$141.32	13.150%	$159.9036	$159.90	$159.90	$159.90
Purchase #5	$39.45	3.658%	$40.8931	$40.89	$40.90	$40.90
Purchase #6	$201.84	9.840%	$221.7011	$221.70	$221.70	$221.70
Purchase #7	$235.89	3.456%	$244.0424	$244.04	$244.05	$244.00
7 purchase totals =	$992.50		$1,073.9695	$1,073.95	$1,074.00	$1,074.00