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	$138.47	10.108%	$152.4665	$152.47	$152.45	$152.50
Purchase #2	$60.94	10.777%	$67.5075	$67.51	$67.50	$67.50
Purchase #3	$135.56	12.381%	$152.3437	$152.34	$152.35	$152.30
Purchase #4	$205.96	10.279%	$227.1306	$227.13	$227.15	$227.10
Purchase #5	$145.61	13.363%	$165.0679	$165.07	$165.05	$165.10
Purchase #6	$40.28	10.263%	$44.4139	$44.41	$44.40	$44.40
Purchase #7	$157.58	7.718%	$169.742	$169.74	$169.75	$169.70
7 purchase totals =	$884.40		$978.6721	$978.67	$978.65	$978.60