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	$171.94	13.369%	$194.9267	$194.93	$194.95	$194.90
Purchase #2	$95.33	3.299%	$98.4749	$98.47	$98.45	$98.50
Purchase #3	$111.83	13.199%	$126.5904	$126.59	$126.60	$126.60
Purchase #4	$236.77	3.374%	$244.7586	$244.76	$244.75	$244.80
Purchase #5	$132.46	13.377%	$150.1792	$150.18	$150.20	$150.20
Purchase #6	$160.34	9.773%	$176.01	$176.01	$176.00	$176.00
Purchase #7	$132.46	11.787%	$148.0731	$148.07	$148.05	$148.10
7 purchase totals =	$1,041.13		$1,139.0129	$1,139.01	$1,139.00	$1,139.10