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	$98.25	3.385%	$101.5758	$101.58	$101.60	$101.60
Purchase #2	$20.76	3.318%	$21.4488	$21.45	$21.45	$21.40
Purchase #3	$215.53	11.455%	$240.219	$240.22	$240.20	$240.20
Purchase #4	$17.67	4.572%	$18.4779	$18.48	$18.50	$18.50
Purchase #5	$171.34	9.580%	$187.7544	$187.75	$187.75	$187.80
Purchase #6	$228.33	11.685%	$255.0104	$255.01	$255.00	$255.00
Purchase #7	$80.83	3.766%	$83.8741	$83.87	$83.85	$83.90
7 purchase totals =	$832.71		$908.3604	$908.36	$908.35	$908.40