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	$125.50	5.116%	$131.9206	$131.92	$131.90	$131.90
Purchase #2	$89.92	8.514%	$97.5758	$97.58	$97.60	$97.60
Purchase #3	$208.32	10.845%	$230.9123	$230.91	$230.90	$230.90
Purchase #4	$105.81	6.721%	$112.9215	$112.92	$112.90	$112.90
Purchase #5	$145.66	3.187%	$150.3022	$150.30	$150.30	$150.30
Purchase #6	$101.79	11.482%	$113.4775	$113.48	$113.50	$113.50
Purchase #7	$151.63	9.409%	$165.8969	$165.90	$165.90	$165.90
7 purchase totals =	$928.63		$1,003.0068	$1,003.01	$1,003.00	$1,003.00