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	$160.34	6.776%	$171.2046	$171.20	$171.20	$171.20
Purchase #2	$227.89	13.398%	$258.4227	$258.42	$258.40	$258.40
Purchase #3	$111.80	7.814%	$120.5361	$120.54	$120.55	$120.50
Purchase #4	$231.38	10.526%	$255.7351	$255.74	$255.75	$255.70
Purchase #5	$230.99	13.809%	$262.8874	$262.89	$262.90	$262.90
Purchase #6	$243.35	11.147%	$270.4762	$270.48	$270.50	$270.50
Purchase #7	$155.25	4.847%	$162.775	$162.78	$162.80	$162.80
7 purchase totals =	$1,361.00		$1,502.0371	$1,502.05	$1,502.10	$1,502.00