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	$22.87	11.805%	$25.5698	$25.57	$25.55	$25.60
Purchase #2	$140.31	11.103%	$155.8886	$155.89	$155.90	$155.90
Purchase #3	$150.48	13.833%	$171.2959	$171.30	$171.30	$171.30
Purchase #4	$18.64	8.231%	$20.1743	$20.17	$20.15	$20.20
Purchase #5	$161.59	12.692%	$182.099	$182.10	$182.10	$182.10
Purchase #6	$163.81	5.216%	$172.3543	$172.35	$172.35	$172.40
Purchase #7	$23.84	4.142%	$24.8275	$24.83	$24.85	$24.80
7 purchase totals =	$681.54		$752.2094	$752.21	$752.20	$752.30