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	$111.27	5.484%	$117.372	$117.37	$117.35	$117.40
Purchase #2	$150.48	12.231%	$168.8852	$168.89	$168.90	$168.90
Purchase #3	$192.86	7.694%	$207.6986	$207.70	$207.70	$207.70
Purchase #4	$206.80	11.755%	$231.1093	$231.11	$231.10	$231.10
Purchase #5	$138.73	8.478%	$150.4915	$150.49	$150.50	$150.50
Purchase #6	$87.78	4.333%	$91.5835	$91.58	$91.60	$91.60
Purchase #7	$79.95	13.450%	$90.7033	$90.70	$90.70	$90.70
7 purchase totals =	$967.87		$1,057.8434	$1,057.84	$1,057.85	$1,057.90