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	$152.35	13.132%	$172.3566	$172.36	$172.35	$172.40
Purchase #2	$138.29	9.197%	$151.0085	$151.01	$151.00	$151.00
Purchase #3	$143.58	9.118%	$156.6716	$156.67	$156.65	$156.70
Purchase #4	$127.89	13.814%	$145.5567	$145.56	$145.55	$145.60
Purchase #5	$231.97	7.319%	$248.9479	$248.95	$248.95	$248.90
Purchase #6	$179.99	5.764%	$190.3646	$190.36	$190.35	$190.40
Purchase #7	$19.59	5.410%	$20.6498	$20.65	$20.65	$20.60
7 purchase totals =	$993.66		$1,085.5557	$1,085.56	$1,085.50	$1,085.60