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	$183.29	4.407%	$191.3676	$191.37	$191.35	$191.40
Purchase #2	$130.30	5.635%	$137.6424	$137.64	$137.65	$137.60
Purchase #3	$69.86	12.336%	$78.4779	$78.48	$78.50	$78.50
Purchase #4	$117.33	12.249%	$131.7018	$131.70	$131.70	$131.70
Purchase #5	$103.44	4.567%	$108.1641	$108.16	$108.15	$108.20
Purchase #6	$56.29	10.237%	$62.0524	$62.05	$62.05	$62.10
Purchase #7	$92.50	5.646%	$97.7226	$97.72	$97.70	$97.70
7 purchase totals =	$753.01		$807.1288	$807.12	$807.10	$807.20