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	$125.29	5.763%	$132.5105	$132.51	$132.50	$132.50
Purchase #2	$70.80	5.685%	$74.825	$74.83	$74.85	$74.80
Purchase #3	$175.76	11.648%	$196.2325	$196.23	$196.25	$196.20
Purchase #4	$176.66	4.753%	$185.0566	$185.06	$185.05	$185.10
Purchase #5	$210.78	12.193%	$236.4804	$236.48	$236.50	$236.50
Purchase #6	$221.87	12.321%	$249.2066	$249.21	$249.20	$249.20
Purchase #7	$70.29	3.706%	$72.8949	$72.89	$72.90	$72.90
7 purchase totals =	$1,051.45		$1,147.2065	$1,147.21	$1,147.25	$1,147.20