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	$42.82	5.456%	$45.1563	$45.16	$45.15	$45.20
Purchase #2	$142.78	13.487%	$162.0367	$162.04	$162.05	$162.00
Purchase #3	$60.66	11.848%	$67.847	$67.85	$67.85	$67.80
Purchase #4	$161.68	10.615%	$178.8423	$178.84	$178.85	$178.80
Purchase #5	$199.37	7.224%	$213.7725	$213.77	$213.75	$213.80
Purchase #6	$205.30	12.644%	$231.2581	$231.26	$231.25	$231.30
Purchase #7	$227.39	7.113%	$243.5643	$243.56	$243.55	$243.60
7 purchase totals =	$1,040.00		$1,142.4772	$1,142.48	$1,142.45	$1,142.50