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	$100.37	8.868%	$109.2708	$109.27	$109.25	$109.30
Purchase #2	$194.74	4.472%	$203.4488	$203.45	$203.45	$203.40
Purchase #3	$40.54	6.400%	$43.1346	$43.13	$43.15	$43.10
Purchase #4	$75.44	6.771%	$80.548	$80.55	$80.55	$80.50
Purchase #5	$140.70	3.165%	$145.1532	$145.15	$145.15	$145.20
Purchase #6	$217.56	12.829%	$245.4708	$245.47	$245.45	$245.50
Purchase #7	$95.78	12.647%	$107.8933	$107.89	$107.90	$107.90
7 purchase totals =	$865.13		$934.9195	$934.91	$934.90	$934.90