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	$156.67	7.149%	$167.8703	$167.87	$167.85	$167.90
Purchase #2	$48.43	9.742%	$53.1481	$53.15	$53.15	$53.10
Purchase #3	$169.69	5.811%	$179.5507	$179.55	$179.55	$179.60
Purchase #4	$119.82	5.543%	$126.4616	$126.46	$126.45	$126.50
Purchase #5	$95.97	6.764%	$102.4614	$102.46	$102.45	$102.50
Purchase #6	$204.47	9.313%	$223.5123	$223.51	$223.50	$223.50
Purchase #7	$134.37	8.305%	$145.5294	$145.53	$145.55	$145.50
7 purchase totals =	$929.42		$998.5338	$998.53	$998.50	$998.60