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	$133.83	6.215%	$142.1475	$142.15	$142.15	$142.10
Purchase #2	$50.59	7.693%	$54.4819	$54.48	$54.50	$54.50
Purchase #3	$223.34	10.745%	$247.3379	$247.34	$247.35	$247.30
Purchase #4	$16.90	12.184%	$18.9591	$18.96	$18.95	$19.00
Purchase #5	$171.75	9.827%	$188.6279	$188.63	$188.65	$188.60
Purchase #6	$153.79	4.204%	$160.2553	$160.26	$160.25	$160.30
Purchase #7	$83.95	10.628%	$92.8722	$92.87	$92.85	$92.90
7 purchase totals =	$834.15		$904.6818	$904.69	$904.70	$904.70