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	$29.93	7.804%	$32.2657	$32.27	$32.25	$32.30
Purchase #2	$179.82	3.175%	$185.5293	$185.53	$185.55	$185.50
Purchase #3	$231.27	10.859%	$256.3836	$256.38	$256.40	$256.40
Purchase #4	$117.50	11.104%	$130.5472	$130.55	$130.55	$130.50
Purchase #5	$235.77	10.741%	$261.0941	$261.09	$261.10	$261.10
Purchase #6	$91.28	7.487%	$98.1141	$98.11	$98.10	$98.10
Purchase #7	$125.41	5.311%	$132.0705	$132.07	$132.05	$132.10
7 purchase totals =	$1,010.98		$1,096.0045	$1,096.00	$1,096.00	$1,096.00