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	$21.79	3.154%	$22.4773	$22.48	$22.50	$22.50
Purchase #2	$152.93	6.155%	$162.3428	$162.34	$162.35	$162.30
Purchase #3	$138.75	8.725%	$150.8559	$150.86	$150.85	$150.90
Purchase #4	$50.90	8.194%	$55.0707	$55.07	$55.05	$55.10
Purchase #5	$178.51	5.178%	$187.7532	$187.75	$187.75	$187.80
Purchase #6	$180.34	4.515%	$188.4824	$188.48	$188.50	$188.50
Purchase #7	$236.33	5.136%	$248.4679	$248.47	$248.45	$248.50
7 purchase totals =	$959.55		$1,015.4502	$1,015.45	$1,015.45	$1,015.60