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	$144.62	3.796%	$150.1098	$150.11	$150.10	$150.10
Purchase #2	$181.85	12.869%	$205.2523	$205.25	$205.25	$205.30
Purchase #3	$98.96	12.692%	$111.52	$111.52	$111.50	$111.50
Purchase #4	$42.34	4.873%	$44.4032	$44.40	$44.40	$44.40
Purchase #5	$68.25	11.733%	$76.2578	$76.26	$76.25	$76.30
Purchase #6	$131.37	6.868%	$140.3925	$140.39	$140.40	$140.40
Purchase #7	$61.53	9.637%	$67.4596	$67.46	$67.45	$67.50
7 purchase totals =	$728.92		$795.3952	$795.39	$795.35	$795.50