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	$225.33	13.312%	$255.3259	$255.33	$255.35	$255.30
Purchase #2	$67.33	12.723%	$75.8964	$75.90	$75.90	$75.90
Purchase #3	$99.54	5.588%	$105.1023	$105.10	$105.10	$105.10
Purchase #4	$172.58	12.738%	$194.5632	$194.56	$194.55	$194.60
Purchase #5	$227.32	7.577%	$244.544	$244.54	$244.55	$244.50
Purchase #6	$42.59	5.868%	$45.0892	$45.09	$45.10	$45.10
Purchase #7	$72.74	4.385%	$75.9296	$75.93	$75.95	$75.90
7 purchase totals =	$907.43		$996.4506	$996.45	$996.50	$996.40