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	$147.38	11.394%	$164.1725	$164.17	$164.15	$164.20
Purchase #2	$232.84	3.367%	$240.6797	$240.68	$240.70	$240.70
Purchase #3	$41.79	4.381%	$43.6208	$43.62	$43.60	$43.60
Purchase #4	$87.26	13.289%	$98.856	$98.86	$98.85	$98.90
Purchase #5	$90.75	10.791%	$100.5428	$100.54	$100.55	$100.50
Purchase #6	$222.75	12.584%	$250.7809	$250.78	$250.80	$250.80
Purchase #7	$197.62	13.242%	$223.7888	$223.79	$223.80	$223.80
7 purchase totals =	$1,020.39		$1,122.4415	$1,122.44	$1,122.45	$1,122.50