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	$41.85	4.762%	$43.8429	$43.84	$43.85	$43.80
Purchase #2	$185.57	11.501%	$206.9124	$206.91	$206.90	$206.90
Purchase #3	$165.67	4.116%	$172.489	$172.49	$172.50	$172.50
Purchase #4	$107.67	7.828%	$116.0984	$116.10	$116.10	$116.10
Purchase #5	$247.72	3.475%	$256.3283	$256.33	$256.35	$256.30
Purchase #6	$87.78	12.688%	$98.9175	$98.92	$98.90	$98.90
Purchase #7	$114.33	9.363%	$125.0347	$125.03	$125.05	$125.00
7 purchase totals =	$950.59		$1,019.6232	$1,019.62	$1,019.65	$1,019.50