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	$50.72	6.744%	$54.1406	$54.14	$54.15	$54.10
Purchase #2	$10.85	7.844%	$11.7011	$11.70	$11.70	$11.70
Purchase #3	$247.32	3.660%	$256.3719	$256.37	$256.35	$256.40
Purchase #4	$98.49	13.347%	$111.6355	$111.64	$111.65	$111.60
Purchase #5	$152.89	7.290%	$164.0357	$164.04	$164.05	$164.00
Purchase #6	$227.59	12.864%	$256.8672	$256.87	$256.85	$256.90
Purchase #7	$30.45	10.821%	$33.745	$33.75	$33.75	$33.70
7 purchase totals =	$818.31		$888.4970	$888.51	$888.50	$888.40