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	$226.44	11.541%	$252.5734	$252.57	$252.55	$252.60
Purchase #2	$141.32	13.717%	$160.7049	$160.70	$160.70	$160.70
Purchase #3	$66.48	8.506%	$72.1348	$72.13	$72.15	$72.10
Purchase #4	$174.32	9.716%	$191.2569	$191.26	$191.25	$191.30
Purchase #5	$61.78	7.186%	$66.2195	$66.22	$66.20	$66.20
Purchase #6	$36.89	9.807%	$40.5078	$40.51	$40.50	$40.50
Purchase #7	$86.87	6.396%	$92.4262	$92.43	$92.45	$92.40
7 purchase totals =	$794.10		$875.8235	$875.82	$875.80	$875.80