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	$131.60	4.190%	$137.114	$137.11	$137.10	$137.10
Purchase #2	$110.86	8.261%	$120.0181	$120.02	$120.00	$120.00
Purchase #3	$100.78	10.298%	$111.1583	$111.16	$111.15	$111.20
Purchase #4	$35.28	12.654%	$39.7443	$39.74	$39.75	$39.70
Purchase #5	$228.45	4.414%	$238.5338	$238.53	$238.55	$238.50
Purchase #6	$129.40	7.267%	$138.8035	$138.80	$138.80	$138.80
Purchase #7	$237.89	11.197%	$264.5265	$264.53	$264.55	$264.50
7 purchase totals =	$974.26		$1,049.8985	$1,049.89	$1,049.90	$1,049.80