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	$199.29	10.218%	$219.6535	$219.65	$219.65	$219.70
Purchase #2	$130.73	12.443%	$146.9967	$147.00	$147.00	$147.00
Purchase #3	$35.39	5.835%	$37.455	$37.46	$37.45	$37.50
Purchase #4	$67.34	9.283%	$73.5912	$73.59	$73.60	$73.60
Purchase #5	$18.55	5.369%	$19.5459	$19.55	$19.55	$19.50
Purchase #6	$20.75	4.830%	$21.7522	$21.75	$21.75	$21.80
Purchase #7	$38.82	4.532%	$40.5793	$40.58	$40.60	$40.60
7 purchase totals =	$510.87		$559.5738	$559.58	$559.60	$559.70