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	$169.42	6.525%	$180.4747	$180.47	$180.45	$180.50
Purchase #2	$88.36	12.478%	$99.3856	$99.39	$99.40	$99.40
Purchase #3	$105.86	11.359%	$117.8846	$117.88	$117.90	$117.90
Purchase #4	$121.87	12.754%	$137.4133	$137.41	$137.40	$137.40
Purchase #5	$80.41	3.547%	$83.2621	$83.26	$83.25	$83.30
Purchase #6	$218.32	5.273%	$229.832	$229.83	$229.85	$229.80
Purchase #7	$73.39	7.487%	$78.8847	$78.88	$78.90	$78.90
7 purchase totals =	$857.63		$927.1370	$927.12	$927.15	$927.20