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	$105.61	5.871%	$111.8104	$111.81	$111.80	$111.80
Purchase #2	$153.73	7.240%	$164.8601	$164.86	$164.85	$164.90
Purchase #3	$199.29	10.746%	$220.7057	$220.71	$220.70	$220.70
Purchase #4	$89.56	9.820%	$98.3548	$98.35	$98.35	$98.40
Purchase #5	$101.89	3.690%	$105.6497	$105.65	$105.65	$105.60
Purchase #6	$88.75	9.332%	$97.0322	$97.03	$97.05	$97.00
Purchase #7	$224.32	6.313%	$238.4813	$238.48	$238.50	$238.50
7 purchase totals =	$963.15		$1,036.8942	$1,036.89	$1,036.90	$1,036.90