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	$196.69	10.761%	$217.8558	$217.86	$217.85	$217.90
Purchase #2	$156.77	9.679%	$171.9438	$171.94	$171.95	$171.90
Purchase #3	$165.85	3.211%	$171.1754	$171.18	$171.20	$171.20
Purchase #4	$66.29	9.197%	$72.3867	$72.39	$72.40	$72.40
Purchase #5	$11.57	11.616%	$12.914	$12.91	$12.90	$12.90
Purchase #6	$67.27	10.775%	$74.5183	$74.52	$74.50	$74.50
Purchase #7	$176.56	9.808%	$193.877	$193.88	$193.90	$193.90
7 purchase totals =	$841.00		$914.6710	$914.68	$914.70	$914.70