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	$228.71	11.585%	$255.2061	$255.21	$255.20	$255.20
Purchase #2	$125.77	13.205%	$142.3779	$142.38	$142.40	$142.40
Purchase #3	$195.90	11.155%	$217.7526	$217.75	$217.75	$217.80
Purchase #4	$39.70	13.770%	$45.1667	$45.17	$45.15	$45.20
Purchase #5	$191.75	8.480%	$208.0104	$208.01	$208.00	$208.00
Purchase #6	$169.53	11.398%	$188.853	$188.85	$188.85	$188.90
Purchase #7	$26.86	13.694%	$30.5382	$30.54	$30.55	$30.50
7 purchase totals =	$978.22		$1,087.9049	$1,087.91	$1,087.90	$1,088.00