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	$194.64	12.430%	$218.8338	$218.83	$218.85	$218.80
Purchase #2	$12.80	13.325%	$14.5056	$14.51	$14.50	$14.50
Purchase #3	$211.82	12.515%	$238.3293	$238.33	$238.35	$238.30
Purchase #4	$88.28	12.792%	$99.5728	$99.57	$99.55	$99.60
Purchase #5	$192.54	11.793%	$215.2462	$215.25	$215.25	$215.20
Purchase #6	$126.94	9.583%	$139.1047	$139.10	$139.10	$139.10
Purchase #7	$108.61	3.589%	$112.508	$112.51	$112.50	$112.50
7 purchase totals =	$935.63		$1,038.1004	$1,038.10	$1,038.10	$1,038.00