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	$171.87	10.267%	$189.5159	$189.52	$189.50	$189.50
Purchase #2	$238.86	6.779%	$255.0523	$255.05	$255.05	$255.10
Purchase #3	$246.90	7.846%	$266.2718	$266.27	$266.25	$266.30
Purchase #4	$178.85	9.508%	$195.8551	$195.86	$195.85	$195.90
Purchase #5	$145.82	10.560%	$161.2186	$161.22	$161.20	$161.20
Purchase #6	$91.79	13.858%	$104.5103	$104.51	$104.50	$104.50
Purchase #7	$7.34	12.850%	$8.2832	$8.28	$8.30	$8.30
7 purchase totals =	$1,081.43		$1,180.7072	$1,180.71	$1,180.65	$1,180.80