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	$241.88	9.309%	$264.3966	$264.40	$264.40	$264.40
Purchase #2	$76.90	10.869%	$85.2583	$85.26	$85.25	$85.30
Purchase #3	$137.42	10.814%	$152.2806	$152.28	$152.30	$152.30
Purchase #4	$204.38	5.853%	$216.3424	$216.34	$216.35	$216.30
Purchase #5	$203.73	9.576%	$223.2392	$223.24	$223.25	$223.20
Purchase #6	$77.25	6.311%	$82.1252	$82.13	$82.15	$82.10
Purchase #7	$53.63	9.590%	$58.7731	$58.77	$58.75	$58.80
7 purchase totals =	$995.19		$1,082.4154	$1,082.42	$1,082.45	$1,082.40