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	$139.89	9.467%	$153.1334	$153.13	$153.15	$153.10
Purchase #2	$142.43	5.223%	$149.8691	$149.87	$149.85	$149.90
Purchase #3	$46.26	13.476%	$52.494	$52.49	$52.50	$52.50
Purchase #4	$127.86	11.872%	$143.0395	$143.04	$143.05	$143.00
Purchase #5	$242.68	12.228%	$272.3549	$272.35	$272.35	$272.40
Purchase #6	$52.69	12.146%	$59.0897	$59.09	$59.10	$59.10
Purchase #7	$231.84	6.493%	$246.8934	$246.89	$246.90	$246.90
7 purchase totals =	$983.65		$1,076.8740	$1,076.86	$1,076.90	$1,076.90