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	$77.88	13.451%	$88.3556	$88.36	$88.35	$88.40
Purchase #2	$113.66	8.642%	$123.4825	$123.48	$123.50	$123.50
Purchase #3	$42.43	8.162%	$45.8931	$45.89	$45.90	$45.90
Purchase #4	$172.84	5.317%	$182.0299	$182.03	$182.05	$182.00
Purchase #5	$225.60	10.543%	$249.385	$249.39	$249.40	$249.40
Purchase #6	$218.76	4.184%	$227.9129	$227.91	$227.90	$227.90
Purchase #7	$176.82	12.742%	$199.3504	$199.35	$199.35	$199.40
7 purchase totals =	$1,027.99		$1,116.4094	$1,116.41	$1,116.45	$1,116.50