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	$151.55	10.342%	$167.2233	$167.22	$167.20	$167.20
Purchase #2	$247.49	7.143%	$265.1682	$265.17	$265.15	$265.20
Purchase #3	$169.32	5.344%	$178.3685	$178.37	$178.35	$178.40
Purchase #4	$162.82	4.482%	$170.1176	$170.12	$170.10	$170.10
Purchase #5	$59.39	11.741%	$66.363	$66.36	$66.35	$66.40
Purchase #6	$76.92	11.601%	$85.8435	$85.84	$85.85	$85.80
Purchase #7	$46.75	7.495%	$50.2539	$50.25	$50.25	$50.30
7 purchase totals =	$914.24		$983.3380	$983.33	$983.25	$983.40