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	$170.51	12.483%	$191.7948	$191.79	$191.80	$191.80
Purchase #2	$19.65	8.859%	$21.3908	$21.39	$21.40	$21.40
Purchase #3	$179.38	7.309%	$192.4909	$192.49	$192.50	$192.50
Purchase #4	$242.71	5.513%	$256.0906	$256.09	$256.10	$256.10
Purchase #5	$68.63	7.310%	$73.6469	$73.65	$73.65	$73.60
Purchase #6	$191.81	13.867%	$218.4083	$218.41	$218.40	$218.40
Purchase #7	$82.78	9.410%	$90.5696	$90.57	$90.55	$90.60
7 purchase totals =	$955.47		$1,044.3919	$1,044.39	$1,044.40	$1,044.40