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	$208.37	4.743%	$218.253	$218.25	$218.25	$218.30
Purchase #2	$250.59	4.484%	$261.8265	$261.83	$261.85	$261.80
Purchase #3	$143.73	3.496%	$148.7548	$148.75	$148.75	$148.80
Purchase #4	$145.61	3.778%	$151.1111	$151.11	$151.10	$151.10
Purchase #5	$17.45	8.150%	$18.8722	$18.87	$18.85	$18.90
Purchase #6	$8.43	10.619%	$9.3252	$9.33	$9.35	$9.30
Purchase #7	$178.86	9.178%	$195.2758	$195.28	$195.30	$195.30
7 purchase totals =	$953.04		$1,003.4186	$1,003.42	$1,003.45	$1,003.50