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	$52.37	13.830%	$59.6128	$59.61	$59.60	$59.60
Purchase #2	$6.28	7.418%	$6.7459	$6.75	$6.75	$6.70
Purchase #3	$157.89	13.783%	$179.652	$179.65	$179.65	$179.70
Purchase #4	$245.73	6.105%	$260.7318	$260.73	$260.75	$260.70
Purchase #5	$151.86	8.542%	$164.8319	$164.83	$164.85	$164.80
Purchase #6	$88.87	10.439%	$98.1471	$98.15	$98.15	$98.10
Purchase #7	$133.32	11.184%	$148.2305	$148.23	$148.25	$148.20
7 purchase totals =	$836.32		$917.9520	$917.95	$918.00	$917.80