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	$208.83	3.863%	$216.8971	$216.90	$216.90	$216.90
Purchase #2	$149.49	4.361%	$156.0093	$156.01	$156.00	$156.00
Purchase #3	$92.71	5.867%	$98.1493	$98.15	$98.15	$98.10
Purchase #4	$92.51	7.414%	$99.3687	$99.37	$99.35	$99.40
Purchase #5	$185.51	5.373%	$195.4775	$195.48	$195.50	$195.50
Purchase #6	$34.71	10.870%	$38.483	$38.48	$38.50	$38.50
Purchase #7	$221.36	13.630%	$251.5314	$251.53	$251.55	$251.50
7 purchase totals =	$985.12		$1,055.9163	$1,055.92	$1,055.95	$1,055.90