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	$243.78	4.843%	$255.5863	$255.59	$255.60	$255.60
Purchase #2	$62.95	12.328%	$70.7105	$70.71	$70.70	$70.70
Purchase #3	$91.53	13.805%	$104.1657	$104.17	$104.15	$104.20
Purchase #4	$202.51	3.799%	$210.2034	$210.20	$210.20	$210.20
Purchase #5	$57.91	3.480%	$59.9253	$59.93	$59.95	$59.90
Purchase #6	$22.50	8.399%	$24.3898	$24.39	$24.40	$24.40
Purchase #7	$210.51	11.320%	$234.3397	$234.34	$234.35	$234.30
7 purchase totals =	$891.69		$959.3207	$959.33	$959.35	$959.30