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	$101.37	12.490%	$114.0311	$114.03	$114.05	$114.00
Purchase #2	$33.95	9.303%	$37.1084	$37.11	$37.10	$37.10
Purchase #3	$122.71	6.795%	$131.0481	$131.05	$131.05	$131.00
Purchase #4	$166.98	8.311%	$180.8577	$180.86	$180.85	$180.90
Purchase #5	$76.88	7.553%	$82.6867	$82.69	$82.70	$82.70
Purchase #6	$128.88	13.427%	$146.1847	$146.18	$146.20	$146.20
Purchase #7	$93.75	10.126%	$103.2431	$103.24	$103.25	$103.20
7 purchase totals =	$724.52		$795.1598	$795.16	$795.20	$795.10