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	$155.30	7.725%	$167.2969	$167.30	$167.30	$167.30
Purchase #2	$175.50	5.702%	$185.507	$185.51	$185.50	$185.50
Purchase #3	$187.57	12.246%	$210.5398	$210.54	$210.55	$210.50
Purchase #4	$223.76	8.800%	$243.4509	$243.45	$243.45	$243.50
Purchase #5	$219.49	4.126%	$228.5462	$228.55	$228.55	$228.50
Purchase #6	$91.49	3.720%	$94.8934	$94.89	$94.90	$94.90
Purchase #7	$108.26	13.630%	$123.0158	$123.02	$123.00	$123.00
7 purchase totals =	$1,161.37		$1,253.2500	$1,253.26	$1,253.25	$1,253.20