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	$63.63	11.443%	$70.9112	$70.91	$70.90	$70.90
Purchase #2	$146.26	11.150%	$162.568	$162.57	$162.55	$162.60
Purchase #3	$44.77	3.790%	$46.4668	$46.47	$46.45	$46.50
Purchase #4	$200.84	4.197%	$209.2693	$209.27	$209.25	$209.30
Purchase #5	$52.92	12.205%	$59.3789	$59.38	$59.40	$59.40
Purchase #6	$199.56	11.174%	$221.8588	$221.86	$221.85	$221.90
Purchase #7	$159.39	12.176%	$178.7973	$178.80	$178.80	$178.80
7 purchase totals =	$867.37		$949.2503	$949.26	$949.20	$949.40