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	$87.26	6.468%	$92.904	$92.90	$92.90	$92.90
Purchase #2	$233.54	9.537%	$255.8127	$255.81	$255.80	$255.80
Purchase #3	$86.38	9.816%	$94.8591	$94.86	$94.85	$94.90
Purchase #4	$33.87	7.327%	$36.3517	$36.35	$36.35	$36.40
Purchase #5	$225.86	12.437%	$253.9502	$253.95	$253.95	$254.00
Purchase #6	$30.98	6.253%	$32.9172	$32.92	$32.90	$32.90
Purchase #7	$206.56	13.697%	$234.8525	$234.85	$234.85	$234.90
7 purchase totals =	$904.45		$1,001.6474	$1,001.64	$1,001.60	$1,001.80