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	$50.94	7.127%	$54.5705	$54.57	$54.55	$54.60
Purchase #2	$39.32	13.576%	$44.6581	$44.66	$44.65	$44.70
Purchase #3	$18.97	12.360%	$21.3147	$21.31	$21.30	$21.30
Purchase #4	$21.30	9.714%	$23.3691	$23.37	$23.35	$23.40
Purchase #5	$177.29	7.873%	$191.248	$191.25	$191.25	$191.20
Purchase #6	$44.39	5.451%	$46.8097	$46.81	$46.80	$46.80
Purchase #7	$55.65	10.143%	$61.2946	$61.29	$61.30	$61.30
7 purchase totals =	$407.86		$443.2647	$443.26	$443.20	$443.30