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	$171.98	12.256%	$193.0579	$193.06	$193.05	$193.10
Purchase #2	$191.91	10.188%	$211.4618	$211.46	$211.45	$211.50
Purchase #3	$175.77	13.547%	$199.5816	$199.58	$199.60	$199.60
Purchase #4	$153.67	5.540%	$162.1833	$162.18	$162.20	$162.20
Purchase #5	$32.53	3.484%	$33.6633	$33.66	$33.65	$33.70
Purchase #6	$175.87	11.713%	$196.4697	$196.47	$196.45	$196.50
Purchase #7	$131.72	12.538%	$148.2351	$148.24	$148.25	$148.20
7 purchase totals =	$1,033.45		$1,144.6527	$1,144.65	$1,144.65	$1,144.80