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	$177.26	8.527%	$192.375	$192.38	$192.40	$192.40
Purchase #2	$80.64	10.841%	$89.3822	$89.38	$89.40	$89.40
Purchase #3	$244.64	4.457%	$255.5436	$255.54	$255.55	$255.50
Purchase #4	$15.93	7.273%	$17.0886	$17.09	$17.10	$17.10
Purchase #5	$130.51	13.321%	$147.8952	$147.90	$147.90	$147.90
Purchase #6	$168.63	3.776%	$174.9975	$175.00	$175.00	$175.00
Purchase #7	$122.77	7.134%	$131.5284	$131.53	$131.55	$131.50
7 purchase totals =	$940.38		$1,008.8105	$1,008.82	$1,008.90	$1,008.80