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	$187.59	9.372%	$205.1709	$205.17	$205.15	$205.20
Purchase #2	$233.61	8.663%	$253.8476	$253.85	$253.85	$253.80
Purchase #3	$40.43	3.754%	$41.9477	$41.95	$41.95	$41.90
Purchase #4	$128.76	9.143%	$140.5325	$140.53	$140.55	$140.50
Purchase #5	$179.87	11.703%	$200.9202	$200.92	$200.90	$200.90
Purchase #6	$112.50	5.440%	$118.62	$118.62	$118.60	$118.60
Purchase #7	$33.97	10.226%	$37.4438	$37.44	$37.45	$37.40
7 purchase totals =	$916.73		$998.4827	$998.48	$998.45	$998.30