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	$216.55	13.578%	$245.9532	$245.95	$245.95	$246.00
Purchase #2	$109.55	6.423%	$116.5864	$116.59	$116.60	$116.60
Purchase #3	$109.43	8.634%	$118.8782	$118.88	$118.90	$118.90
Purchase #4	$129.82	10.150%	$142.9967	$143.00	$143.00	$143.00
Purchase #5	$60.72	10.371%	$67.0173	$67.02	$67.00	$67.00
Purchase #6	$224.48	8.760%	$244.1444	$244.14	$244.15	$244.10
Purchase #7	$90.69	4.143%	$94.4473	$94.45	$94.45	$94.40
7 purchase totals =	$941.24		$1,030.0235	$1,030.03	$1,030.05	$1,030.00