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	$226.35	7.721%	$243.8265	$243.83	$243.85	$243.80
Purchase #2	$145.89	4.220%	$152.0466	$152.05	$152.05	$152.00
Purchase #3	$112.52	12.743%	$126.8584	$126.86	$126.85	$126.90
Purchase #4	$69.59	11.644%	$77.6931	$77.69	$77.70	$77.70
Purchase #5	$40.43	12.125%	$45.3321	$45.33	$45.35	$45.30
Purchase #6	$143.45	8.224%	$155.2473	$155.25	$155.25	$155.20
Purchase #7	$237.93	6.332%	$252.9957	$253.00	$253.00	$253.00
7 purchase totals =	$976.16		$1,053.9997	$1,054.01	$1,054.05	$1,053.90