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	$9.65	8.733%	$10.4927	$10.49	$10.50	$10.50
Purchase #2	$199.35	3.200%	$205.7292	$205.73	$205.75	$205.70
Purchase #3	$72.36	13.770%	$82.324	$82.32	$82.30	$82.30
Purchase #4	$89.79	8.805%	$97.696	$97.70	$97.70	$97.70
Purchase #5	$164.55	10.830%	$182.3708	$182.37	$182.35	$182.40
Purchase #6	$227.45	5.717%	$240.4533	$240.45	$240.45	$240.50
Purchase #7	$168.72	8.530%	$183.1118	$183.11	$183.10	$183.10
7 purchase totals =	$931.87		$1,002.1778	$1,002.17	$1,002.15	$1,002.20