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	$85.56	7.817%	$92.2482	$92.25	$92.25	$92.20
Purchase #2	$42.77	13.317%	$48.4657	$48.47	$48.45	$48.50
Purchase #3	$50.70	11.667%	$56.6152	$56.62	$56.60	$56.60
Purchase #4	$113.37	13.102%	$128.2237	$128.22	$128.20	$128.20
Purchase #5	$72.56	8.281%	$78.5687	$78.57	$78.55	$78.60
Purchase #6	$199.39	11.686%	$222.6907	$222.69	$222.70	$222.70
Purchase #7	$175.90	8.701%	$191.2051	$191.21	$191.20	$191.20
7 purchase totals =	$740.25		$818.0173	$818.03	$817.95	$818.00