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	$170.70	6.331%	$181.507	$181.51	$181.50	$181.50
Purchase #2	$102.84	7.400%	$110.4502	$110.45	$110.45	$110.50
Purchase #3	$125.45	11.243%	$139.5543	$139.55	$139.55	$139.60
Purchase #4	$62.38	8.548%	$67.7122	$67.71	$67.70	$67.70
Purchase #5	$164.87	4.731%	$172.67	$172.67	$172.65	$172.70
Purchase #6	$82.66	3.612%	$85.6457	$85.65	$85.65	$85.60
Purchase #7	$154.90	13.567%	$175.9153	$175.92	$175.90	$175.90
7 purchase totals =	$863.80		$933.4547	$933.46	$933.40	$933.50