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	$206.35	10.347%	$227.701	$227.70	$227.70	$227.70
Purchase #2	$76.67	5.293%	$80.7281	$80.73	$80.75	$80.70
Purchase #3	$197.27	4.817%	$206.7725	$206.77	$206.75	$206.80
Purchase #4	$110.27	12.257%	$123.7858	$123.79	$123.80	$123.80
Purchase #5	$109.67	12.567%	$123.4522	$123.45	$123.45	$123.50
Purchase #6	$37.48	10.604%	$41.4544	$41.45	$41.45	$41.50
Purchase #7	$158.90	5.311%	$167.3392	$167.34	$167.35	$167.30
7 purchase totals =	$896.61		$971.2332	$971.23	$971.25	$971.30