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	$225.89	3.204%	$233.1275	$233.13	$233.15	$233.10
Purchase #2	$11.37	3.492%	$11.767	$11.77	$11.75	$11.80
Purchase #3	$91.89	11.571%	$102.5226	$102.52	$102.50	$102.50
Purchase #4	$176.30	13.274%	$199.7021	$199.70	$199.70	$199.70
Purchase #5	$232.81	6.370%	$247.64	$247.64	$247.65	$247.60
Purchase #6	$98.53	7.368%	$105.7897	$105.79	$105.80	$105.80
Purchase #7	$134.62	3.530%	$139.3721	$139.37	$139.35	$139.40
7 purchase totals =	$971.41		$1,039.9210	$1,039.92	$1,039.90	$1,039.90