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	$107.88	3.531%	$111.6892	$111.69	$111.70	$111.70
Purchase #2	$99.32	12.644%	$111.878	$111.88	$111.90	$111.90
Purchase #3	$179.49	12.388%	$201.7252	$201.73	$201.75	$201.70
Purchase #4	$54.35	6.542%	$57.9056	$57.91	$57.90	$57.90
Purchase #5	$86.46	10.429%	$95.4769	$95.48	$95.50	$95.50
Purchase #6	$27.25	6.593%	$29.0466	$29.05	$29.05	$29.00
Purchase #7	$249.76	4.576%	$261.189	$261.19	$261.20	$261.20
7 purchase totals =	$804.51		$868.9105	$868.93	$869.00	$868.90