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	$154.53	12.632%	$174.0502	$174.05	$174.05	$174.10
Purchase #2	$114.34	13.770%	$130.0846	$130.08	$130.10	$130.10
Purchase #3	$49.96	9.233%	$54.5728	$54.57	$54.55	$54.60
Purchase #4	$41.73	5.213%	$43.9054	$43.91	$43.90	$43.90
Purchase #5	$106.94	4.564%	$111.8207	$111.82	$111.80	$111.80
Purchase #6	$15.56	9.485%	$17.0359	$17.04	$17.05	$17.00
Purchase #7	$32.59	10.498%	$36.0113	$36.01	$36.00	$36.00
7 purchase totals =	$515.65		$567.4809	$567.48	$567.45	$567.50