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	$179.29	12.401%	$201.5238	$201.52	$201.50	$201.50
Purchase #2	$205.98	6.594%	$219.5623	$219.56	$219.55	$219.60
Purchase #3	$134.29	12.182%	$150.6492	$150.65	$150.65	$150.60
Purchase #4	$179.46	6.509%	$191.1411	$191.14	$191.15	$191.10
Purchase #5	$13.92	6.835%	$14.8714	$14.87	$14.85	$14.90
Purchase #6	$204.69	8.796%	$222.6945	$222.69	$222.70	$222.70
Purchase #7	$126.52	3.783%	$131.3063	$131.31	$131.30	$131.30
7 purchase totals =	$1,044.15		$1,131.7486	$1,131.74	$1,131.70	$1,131.70