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	$153.52	3.521%	$158.9254	$158.93	$158.95	$158.90
Purchase #2	$128.27	8.773%	$139.5231	$139.52	$139.50	$139.50
Purchase #3	$135.29	12.384%	$152.0443	$152.04	$152.05	$152.00
Purchase #4	$201.26	6.632%	$214.6076	$214.61	$214.60	$214.60
Purchase #5	$121.90	12.566%	$137.218	$137.22	$137.20	$137.20
Purchase #6	$72.73	7.753%	$78.3688	$78.37	$78.35	$78.40
Purchase #7	$183.77	6.852%	$196.3619	$196.36	$196.35	$196.40
7 purchase totals =	$996.74		$1,077.0491	$1,077.05	$1,077.00	$1,077.00