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	$57.87	6.410%	$61.5795	$61.58	$61.60	$61.60
Purchase #2	$17.67	12.202%	$19.8261	$19.83	$19.85	$19.80
Purchase #3	$138.59	5.569%	$146.3081	$146.31	$146.30	$146.30
Purchase #4	$218.44	13.600%	$248.1478	$248.15	$248.15	$248.10
Purchase #5	$104.43	9.753%	$114.6151	$114.62	$114.60	$114.60
Purchase #6	$189.86	3.739%	$196.9589	$196.96	$196.95	$197.00
Purchase #7	$242.26	8.516%	$262.8909	$262.89	$262.90	$262.90
7 purchase totals =	$969.12		$1,050.3264	$1,050.34	$1,050.35	$1,050.30