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	$91.70	6.281%	$97.4597	$97.46	$97.45	$97.50
Purchase #2	$134.59	11.516%	$150.0894	$150.09	$150.10	$150.10
Purchase #3	$211.82	10.711%	$234.508	$234.51	$234.50	$234.50
Purchase #4	$229.75	6.316%	$244.261	$244.26	$244.25	$244.30
Purchase #5	$11.31	10.725%	$12.523	$12.52	$12.50	$12.50
Purchase #6	$130.60	12.476%	$146.8937	$146.89	$146.90	$146.90
Purchase #7	$116.89	3.837%	$121.3751	$121.38	$121.40	$121.40
7 purchase totals =	$926.66		$1,007.1099	$1,007.11	$1,007.10	$1,007.20