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	$208.78	4.759%	$218.7158	$218.72	$218.70	$218.70
Purchase #2	$177.71	7.682%	$191.3617	$191.36	$191.35	$191.40
Purchase #3	$82.74	10.530%	$91.4525	$91.45	$91.45	$91.50
Purchase #4	$6.73	11.515%	$7.505	$7.51	$7.50	$7.50
Purchase #5	$197.99	9.804%	$217.4009	$217.40	$217.40	$217.40
Purchase #6	$65.54	12.275%	$73.585	$73.59	$73.60	$73.60
Purchase #7	$84.32	5.660%	$89.0925	$89.09	$89.10	$89.10
7 purchase totals =	$823.81		$889.1134	$889.12	$889.10	$889.20