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	$141.33	9.794%	$155.1719	$155.17	$155.15	$155.20
Purchase #2	$111.32	7.398%	$119.5555	$119.56	$119.55	$119.60
Purchase #3	$59.37	8.362%	$64.3345	$64.33	$64.35	$64.30
Purchase #4	$222.59	5.129%	$234.0066	$234.01	$234.00	$234.00
Purchase #5	$133.37	11.639%	$148.8929	$148.89	$148.90	$148.90
Purchase #6	$89.43	6.745%	$95.4621	$95.46	$95.45	$95.50
Purchase #7	$138.67	10.300%	$152.953	$152.95	$152.95	$153.00
7 purchase totals =	$896.08		$970.3765	$970.37	$970.35	$970.50