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	$42.82	5.741%	$45.2783	$45.28	$45.30	$45.30
Purchase #2	$224.94	12.580%	$253.2375	$253.24	$253.25	$253.20
Purchase #3	$135.44	13.601%	$153.8612	$153.86	$153.85	$153.90
Purchase #4	$84.75	5.678%	$89.5621	$89.56	$89.55	$89.60
Purchase #5	$174.81	5.358%	$184.1763	$184.18	$184.20	$184.20
Purchase #6	$166.63	4.307%	$173.8068	$173.81	$173.80	$173.80
Purchase #7	$76.48	8.182%	$82.7376	$82.74	$82.75	$82.70
7 purchase totals =	$905.87		$982.6598	$982.67	$982.70	$982.70