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	$44.91	7.699%	$48.3676	$48.37	$48.35	$48.40
Purchase #2	$215.38	3.230%	$222.3368	$222.34	$222.35	$222.30
Purchase #3	$101.37	3.440%	$104.8571	$104.86	$104.85	$104.90
Purchase #4	$39.48	11.820%	$44.1465	$44.15	$44.15	$44.10
Purchase #5	$142.77	13.390%	$161.8869	$161.89	$161.90	$161.90
Purchase #6	$231.94	10.579%	$256.4769	$256.48	$256.50	$256.50
Purchase #7	$247.52	12.578%	$278.6531	$278.65	$278.65	$278.70
7 purchase totals =	$1,023.37		$1,116.7249	$1,116.74	$1,116.75	$1,116.80