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	$209.72	11.359%	$233.5421	$233.54	$233.55	$233.50
Purchase #2	$82.86	7.318%	$88.9237	$88.92	$88.90	$88.90
Purchase #3	$37.42	8.436%	$40.5768	$40.58	$40.60	$40.60
Purchase #4	$153.56	12.140%	$172.2022	$172.20	$172.20	$172.20
Purchase #5	$106.49	12.279%	$119.5659	$119.57	$119.55	$119.60
Purchase #6	$237.57	7.531%	$255.4614	$255.46	$255.45	$255.50
Purchase #7	$60.53	8.469%	$65.6563	$65.66	$65.65	$65.70
7 purchase totals =	$888.15		$975.9284	$975.93	$975.90	$976.00