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	$97.31	7.853%	$104.9518	$104.95	$104.95	$105.00
Purchase #2	$223.49	9.654%	$245.0657	$245.07	$245.05	$245.10
Purchase #3	$222.89	13.610%	$253.2253	$253.23	$253.25	$253.20
Purchase #4	$104.90	6.417%	$111.6314	$111.63	$111.65	$111.60
Purchase #5	$232.69	8.265%	$251.9218	$251.92	$251.90	$251.90
Purchase #6	$156.60	11.554%	$174.6936	$174.69	$174.70	$174.70
Purchase #7	$101.83	7.392%	$109.3573	$109.36	$109.35	$109.40
7 purchase totals =	$1,139.71		$1,250.8469	$1,250.85	$1,250.85	$1,250.90