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	$215.43	13.816%	$245.1938	$245.19	$245.20	$245.20
Purchase #2	$132.81	4.429%	$138.6922	$138.69	$138.70	$138.70
Purchase #3	$124.27	11.805%	$138.9401	$138.94	$138.95	$138.90
Purchase #4	$123.59	6.663%	$131.8248	$131.82	$131.80	$131.80
Purchase #5	$219.43	12.773%	$247.4578	$247.46	$247.45	$247.50
Purchase #6	$199.70	9.450%	$218.5717	$218.57	$218.55	$218.60
Purchase #7	$36.60	11.711%	$40.8862	$40.89	$40.90	$40.90
7 purchase totals =	$1,051.83		$1,161.5666	$1,161.56	$1,161.55	$1,161.60