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	$169.76	7.693%	$182.8196	$182.82	$182.80	$182.80
Purchase #2	$188.41	10.404%	$208.0122	$208.01	$208.00	$208.00
Purchase #3	$107.42	8.612%	$116.671	$116.67	$116.65	$116.70
Purchase #4	$52.88	3.573%	$54.7694	$54.77	$54.75	$54.80
Purchase #5	$134.69	8.453%	$146.0753	$146.08	$146.10	$146.10
Purchase #6	$133.36	6.321%	$141.7897	$141.79	$141.80	$141.80
Purchase #7	$137.34	11.672%	$153.3703	$153.37	$153.35	$153.40
7 purchase totals =	$923.86		$1,003.5075	$1,003.51	$1,003.45	$1,003.60