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	$76.26	9.490%	$83.4971	$83.50	$83.50	$83.50
Purchase #2	$135.68	11.821%	$151.7187	$151.72	$151.70	$151.70
Purchase #3	$48.97	7.345%	$52.5668	$52.57	$52.55	$52.60
Purchase #4	$118.63	7.705%	$127.7704	$127.77	$127.75	$127.80
Purchase #5	$225.72	13.816%	$256.9055	$256.91	$256.90	$256.90
Purchase #6	$64.35	12.636%	$72.4813	$72.48	$72.50	$72.50
Purchase #7	$19.49	5.516%	$20.5651	$20.57	$20.55	$20.60
7 purchase totals =	$689.10		$765.5049	$765.52	$765.45	$765.60