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	$12.92	11.708%	$14.4327	$14.43	$14.45	$14.40
Purchase #2	$82.60	9.638%	$90.561	$90.56	$90.55	$90.60
Purchase #3	$99.48	11.867%	$111.2853	$111.29	$111.30	$111.30
Purchase #4	$95.98	10.502%	$106.0598	$106.06	$106.05	$106.10
Purchase #5	$179.89	3.696%	$186.5387	$186.54	$186.55	$186.50
Purchase #6	$77.82	12.300%	$87.3919	$87.39	$87.40	$87.40
Purchase #7	$99.61	5.189%	$104.7788	$104.78	$104.80	$104.80
7 purchase totals =	$648.30		$701.0482	$701.05	$701.10	$701.10