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	$40.59	6.795%	$43.3481	$43.35	$43.35	$43.30
Purchase #2	$90.33	6.123%	$95.8609	$95.86	$95.85	$95.90
Purchase #3	$11.33	10.129%	$12.4776	$12.48	$12.50	$12.50
Purchase #4	$77.73	13.641%	$88.3331	$88.33	$88.35	$88.30
Purchase #5	$114.49	8.129%	$123.7969	$123.80	$123.80	$123.80
Purchase #6	$171.25	4.752%	$179.3878	$179.39	$179.40	$179.40
Purchase #7	$243.47	3.421%	$251.7991	$251.80	$251.80	$251.80
7 purchase totals =	$749.19		$795.0035	$795.01	$795.05	$795.00