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	$239.48	5.377%	$252.3568	$252.36	$252.35	$252.40
Purchase #2	$153.54	8.142%	$166.0412	$166.04	$166.05	$166.00
Purchase #3	$85.46	11.419%	$95.2187	$95.22	$95.20	$95.20
Purchase #4	$12.39	7.397%	$13.3065	$13.31	$13.30	$13.30
Purchase #5	$231.47	9.304%	$253.006	$253.01	$253.00	$253.00
Purchase #6	$196.39	11.238%	$218.4603	$218.46	$218.45	$218.50
Purchase #7	$73.60	6.574%	$78.4385	$78.44	$78.45	$78.40
7 purchase totals =	$992.33		$1,076.8280	$1,076.84	$1,076.80	$1,076.80