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	$108.51	13.672%	$123.3455	$123.35	$123.35	$123.30
Purchase #2	$159.48	11.830%	$178.3465	$178.35	$178.35	$178.30
Purchase #3	$52.71	12.501%	$59.2993	$59.30	$59.30	$59.30
Purchase #4	$133.79	3.213%	$138.0887	$138.09	$138.10	$138.10
Purchase #5	$146.28	8.748%	$159.0766	$159.08	$159.10	$159.10
Purchase #6	$161.70	4.427%	$168.8585	$168.86	$168.85	$168.90
Purchase #7	$195.60	13.279%	$221.5737	$221.57	$221.55	$221.60
7 purchase totals =	$958.07		$1,048.5888	$1,048.60	$1,048.60	$1,048.60