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	$93.90	13.485%	$106.5624	$106.56	$106.55	$106.60
Purchase #2	$117.92	10.644%	$130.4714	$130.47	$130.45	$130.50
Purchase #3	$78.71	5.487%	$83.0288	$83.03	$83.05	$83.00
Purchase #4	$50.98	8.691%	$55.4107	$55.41	$55.40	$55.40
Purchase #5	$141.82	8.763%	$154.2477	$154.25	$154.25	$154.20
Purchase #6	$181.91	12.664%	$204.9471	$204.95	$204.95	$204.90
Purchase #7	$248.91	13.315%	$282.0524	$282.05	$282.05	$282.10
7 purchase totals =	$914.15		$1,016.7205	$1,016.72	$1,016.70	$1,016.70