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	$65.31	10.200%	$71.9716	$71.97	$71.95	$72.00
Purchase #2	$71.64	8.144%	$77.4744	$77.47	$77.45	$77.50
Purchase #3	$48.74	9.748%	$53.4912	$53.49	$53.50	$53.50
Purchase #4	$209.32	7.570%	$225.1655	$225.17	$225.15	$225.20
Purchase #5	$220.88	7.819%	$238.1506	$238.15	$238.15	$238.20
Purchase #6	$38.52	10.145%	$42.4279	$42.43	$42.45	$42.40
Purchase #7	$41.81	7.665%	$45.0147	$45.01	$45.00	$45.00
7 purchase totals =	$696.22		$753.6959	$753.69	$753.65	$753.80