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	$238.87	12.792%	$269.4263	$269.43	$269.45	$269.40
Purchase #2	$240.31	12.707%	$270.8462	$270.85	$270.85	$270.80
Purchase #3	$72.73	7.626%	$78.2764	$78.28	$78.30	$78.30
Purchase #4	$73.34	9.443%	$80.2655	$80.27	$80.25	$80.30
Purchase #5	$135.49	7.245%	$145.3063	$145.31	$145.30	$145.30
Purchase #6	$136.28	7.653%	$146.7095	$146.71	$146.70	$146.70
Purchase #7	$5.82	13.764%	$6.6211	$6.62	$6.60	$6.60
7 purchase totals =	$902.84		$997.4513	$997.47	$997.45	$997.40