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	$14.41	8.867%	$15.6877	$15.69	$15.70	$15.70
Purchase #2	$36.80	7.753%	$39.6531	$39.65	$39.65	$39.70
Purchase #3	$236.35	6.166%	$250.9233	$250.92	$250.90	$250.90
Purchase #4	$195.95	13.359%	$222.127	$222.13	$222.15	$222.10
Purchase #5	$75.73	8.547%	$82.2026	$82.20	$82.20	$82.20
Purchase #6	$147.46	3.459%	$152.5606	$152.56	$152.55	$152.60
Purchase #7	$227.49	5.768%	$240.6116	$240.61	$240.60	$240.60
7 purchase totals =	$934.19		$1,003.7659	$1,003.76	$1,003.75	$1,003.80