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	$106.57	4.550%	$111.4189	$111.42	$111.40	$111.40
Purchase #2	$28.33	11.200%	$31.503	$31.50	$31.50	$31.50
Purchase #3	$123.78	13.109%	$140.0063	$140.01	$140.00	$140.00
Purchase #4	$25.64	10.482%	$28.3276	$28.33	$28.35	$28.30
Purchase #5	$137.25	7.351%	$147.3392	$147.34	$147.35	$147.30
Purchase #6	$95.64	3.709%	$99.1873	$99.19	$99.20	$99.20
Purchase #7	$106.36	12.686%	$119.8528	$119.85	$119.85	$119.90
7 purchase totals =	$623.57		$677.6351	$677.64	$677.65	$677.60