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	$213.31	8.712%	$231.8936	$231.89	$231.90	$231.90
Purchase #2	$200.61	6.827%	$214.3056	$214.31	$214.30	$214.30
Purchase #3	$210.40	13.495%	$238.7935	$238.79	$238.80	$238.80
Purchase #4	$21.60	11.588%	$24.103	$24.10	$24.10	$24.10
Purchase #5	$122.90	3.375%	$127.0479	$127.05	$127.05	$127.00
Purchase #6	$145.83	7.185%	$156.3079	$156.31	$156.30	$156.30
Purchase #7	$146.94	8.724%	$159.759	$159.76	$159.75	$159.80
7 purchase totals =	$1,061.59		$1,152.2105	$1,152.21	$1,152.20	$1,152.20