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	$120.87	7.788%	$130.2834	$130.28	$130.30	$130.30
Purchase #2	$223.48	12.452%	$251.3077	$251.31	$251.30	$251.30
Purchase #3	$85.80	8.138%	$92.7824	$92.78	$92.80	$92.80
Purchase #4	$217.26	5.386%	$228.9616	$228.96	$228.95	$229.00
Purchase #5	$100.34	12.715%	$113.0982	$113.10	$113.10	$113.10
Purchase #6	$184.53	6.532%	$196.5835	$196.58	$196.60	$196.60
Purchase #7	$31.38	4.556%	$32.8097	$32.81	$32.80	$32.80
7 purchase totals =	$963.66		$1,045.8265	$1,045.82	$1,045.85	$1,045.90