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	$67.29	5.652%	$71.0932	$71.09	$71.10	$71.10
Purchase #2	$210.35	8.117%	$227.4241	$227.42	$227.40	$227.40
Purchase #3	$204.43	8.549%	$221.9067	$221.91	$221.90	$221.90
Purchase #4	$86.36	9.493%	$94.5582	$94.56	$94.55	$94.60
Purchase #5	$172.83	4.733%	$181.01	$181.01	$181.00	$181.00
Purchase #6	$67.33	8.280%	$72.9049	$72.90	$72.90	$72.90
Purchase #7	$168.31	4.105%	$175.2191	$175.22	$175.20	$175.20
7 purchase totals =	$976.90		$1,044.1162	$1,044.11	$1,044.05	$1,044.10