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	$59.51	10.807%	$65.9412	$65.94	$65.95	$65.90
Purchase #2	$33.70	5.369%	$35.5094	$35.51	$35.50	$35.50
Purchase #3	$212.88	10.282%	$234.7683	$234.77	$234.75	$234.80
Purchase #4	$37.51	12.490%	$42.195	$42.20	$42.20	$42.20
Purchase #5	$84.99	7.736%	$91.5648	$91.56	$91.55	$91.60
Purchase #6	$151.98	13.531%	$172.5444	$172.54	$172.55	$172.50
Purchase #7	$83.67	7.803%	$90.1988	$90.20	$90.20	$90.20
7 purchase totals =	$664.24		$732.7219	$732.72	$732.70	$732.70