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	$233.92	11.124%	$259.9413	$259.94	$259.95	$259.90
Purchase #2	$48.61	11.851%	$54.3708	$54.37	$54.35	$54.40
Purchase #3	$158.44	12.554%	$178.3306	$178.33	$178.35	$178.30
Purchase #4	$242.51	4.523%	$253.4787	$253.48	$253.50	$253.50
Purchase #5	$243.36	3.264%	$251.3033	$251.30	$251.30	$251.30
Purchase #6	$10.92	8.743%	$11.8747	$11.87	$11.85	$11.90
Purchase #7	$74.34	12.268%	$83.46	$83.46	$83.45	$83.50
7 purchase totals =	$1,012.10		$1,092.7594	$1,092.75	$1,092.75	$1,092.80