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	$162.88	7.785%	$175.5602	$175.56	$175.55	$175.60
Purchase #2	$140.55	11.353%	$156.5066	$156.51	$156.50	$156.50
Purchase #3	$244.85	6.551%	$260.8901	$260.89	$260.90	$260.90
Purchase #4	$111.91	10.218%	$123.345	$123.35	$123.35	$123.30
Purchase #5	$23.42	3.588%	$24.2603	$24.26	$24.25	$24.30
Purchase #6	$36.57	5.727%	$38.6644	$38.66	$38.65	$38.70
Purchase #7	$88.60	3.598%	$91.7878	$91.79	$91.80	$91.80
7 purchase totals =	$808.78		$871.0144	$871.02	$871.00	$871.10