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	$30.90	5.688%	$32.6576	$32.66	$32.65	$32.70
Purchase #2	$186.88	13.151%	$211.4566	$211.46	$211.45	$211.50
Purchase #3	$188.43	3.593%	$195.2003	$195.20	$195.20	$195.20
Purchase #4	$39.26	3.281%	$40.5481	$40.55	$40.55	$40.50
Purchase #5	$67.74	5.446%	$71.4291	$71.43	$71.45	$71.40
Purchase #6	$215.61	10.601%	$238.4668	$238.47	$238.45	$238.50
Purchase #7	$231.44	10.431%	$255.5815	$255.58	$255.60	$255.60
7 purchase totals =	$960.26		$1,045.3400	$1,045.35	$1,045.35	$1,045.40