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	$199.85	11.770%	$223.3723	$223.37	$223.35	$223.40
Purchase #2	$45.94	13.224%	$52.0151	$52.02	$52.00	$52.00
Purchase #3	$6.97	11.690%	$7.7848	$7.78	$7.80	$7.80
Purchase #4	$75.42	12.550%	$84.8852	$84.89	$84.90	$84.90
Purchase #5	$61.89	5.681%	$65.406	$65.41	$65.40	$65.40
Purchase #6	$202.45	13.862%	$230.5136	$230.51	$230.50	$230.50
Purchase #7	$73.78	3.381%	$76.2745	$76.27	$76.25	$76.30
7 purchase totals =	$666.30		$740.2515	$740.25	$740.20	$740.30