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	$56.79	12.191%	$63.7133	$63.71	$63.70	$63.70
Purchase #2	$28.87	10.579%	$31.9242	$31.92	$31.90	$31.90
Purchase #3	$32.72	11.635%	$36.527	$36.53	$36.55	$36.50
Purchase #4	$59.95	9.524%	$65.6596	$65.66	$65.65	$65.70
Purchase #5	$180.61	8.544%	$196.0413	$196.04	$196.05	$196.00
Purchase #6	$171.76	11.160%	$190.9284	$190.93	$190.95	$190.90
Purchase #7	$45.65	8.464%	$49.5138	$49.51	$49.50	$49.50
7 purchase totals =	$576.35		$634.3076	$634.30	$634.30	$634.20