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	$70.98	7.178%	$76.0749	$76.07	$76.05	$76.10
Purchase #2	$155.46	11.143%	$172.7829	$172.78	$172.80	$172.80
Purchase #3	$79.90	12.246%	$89.6846	$89.68	$89.70	$89.70
Purchase #4	$111.69	12.317%	$125.4469	$125.45	$125.45	$125.40
Purchase #5	$197.30	6.528%	$210.1797	$210.18	$210.20	$210.20
Purchase #6	$239.37	4.564%	$250.2948	$250.29	$250.30	$250.30
Purchase #7	$116.45	3.517%	$120.5455	$120.55	$120.55	$120.50
7 purchase totals =	$971.15		$1,045.0093	$1,045.00	$1,045.05	$1,045.00