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	$171.57	12.161%	$192.4346	$192.43	$192.45	$192.40
Purchase #2	$226.79	13.800%	$258.087	$258.09	$258.10	$258.10
Purchase #3	$144.43	4.216%	$150.5192	$150.52	$150.50	$150.50
Purchase #4	$245.69	5.642%	$259.5518	$259.55	$259.55	$259.60
Purchase #5	$192.83	3.487%	$199.554	$199.55	$199.55	$199.60
Purchase #6	$244.52	5.636%	$258.3011	$258.30	$258.30	$258.30
Purchase #7	$210.90	5.592%	$222.6935	$222.69	$222.70	$222.70
7 purchase totals =	$1,436.73		$1,541.1412	$1,541.13	$1,541.15	$1,541.20