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	$225.33	13.619%	$256.0177	$256.02	$256.00	$256.00
Purchase #2	$157.90	4.783%	$165.4524	$165.45	$165.45	$165.50
Purchase #3	$198.48	6.545%	$211.4705	$211.47	$211.45	$211.50
Purchase #4	$154.36	4.214%	$160.8647	$160.86	$160.85	$160.90
Purchase #5	$105.85	11.428%	$117.9465	$117.95	$117.95	$117.90
Purchase #6	$75.38	4.870%	$79.051	$79.05	$79.05	$79.10
Purchase #7	$145.68	3.418%	$150.6593	$150.66	$150.65	$150.70
7 purchase totals =	$1,062.98		$1,141.4621	$1,141.46	$1,141.40	$1,141.60