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	$30.54	5.605%	$32.2518	$32.25	$32.25	$32.30
Purchase #2	$35.36	3.815%	$36.709	$36.71	$36.70	$36.70
Purchase #3	$200.69	8.161%	$217.0683	$217.07	$217.05	$217.10
Purchase #4	$16.71	11.619%	$18.6515	$18.65	$18.65	$18.70
Purchase #5	$40.29	5.736%	$42.601	$42.60	$42.60	$42.60
Purchase #6	$71.26	10.375%	$78.6532	$78.65	$78.65	$78.70
Purchase #7	$24.50	4.399%	$25.5778	$25.58	$25.60	$25.60
7 purchase totals =	$419.35		$451.5126	$451.51	$451.50	$451.70