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	$60.90	10.224%	$67.1264	$67.13	$67.15	$67.10
Purchase #2	$202.37	13.105%	$228.8906	$228.89	$228.90	$228.90
Purchase #3	$57.32	9.222%	$62.6061	$62.61	$62.60	$62.60
Purchase #4	$144.94	13.336%	$164.2692	$164.27	$164.25	$164.30
Purchase #5	$148.41	5.580%	$156.6913	$156.69	$156.70	$156.70
Purchase #6	$57.56	13.521%	$65.3427	$65.34	$65.35	$65.30
Purchase #7	$62.42	9.846%	$68.5659	$68.57	$68.55	$68.60
7 purchase totals =	$733.92		$813.4922	$813.50	$813.50	$813.50