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	$200.54	9.466%	$219.5231	$219.52	$219.50	$219.50
Purchase #2	$19.79	11.733%	$22.112	$22.11	$22.10	$22.10
Purchase #3	$202.37	9.658%	$221.9149	$221.91	$221.90	$221.90
Purchase #4	$174.52	12.795%	$196.8498	$196.85	$196.85	$196.80
Purchase #5	$175.79	6.128%	$186.5624	$186.56	$186.55	$186.60
Purchase #6	$217.25	7.383%	$233.2896	$233.29	$233.30	$233.30
Purchase #7	$236.31	3.217%	$243.9121	$243.91	$243.90	$243.90
7 purchase totals =	$1,226.57		$1,324.1639	$1,324.15	$1,324.10	$1,324.10