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	$107.28	7.517%	$115.3442	$115.34	$115.35	$115.30
Purchase #2	$154.31	11.850%	$172.5957	$172.60	$172.60	$172.60
Purchase #3	$64.51	9.730%	$70.7868	$70.79	$70.80	$70.80
Purchase #4	$182.40	4.584%	$190.7612	$190.76	$190.75	$190.80
Purchase #5	$243.46	12.254%	$273.2936	$273.29	$273.30	$273.30
Purchase #6	$90.71	4.857%	$95.1158	$95.12	$95.10	$95.10
Purchase #7	$179.56	10.746%	$198.8555	$198.86	$198.85	$198.90
7 purchase totals =	$1,022.23		$1,116.7528	$1,116.76	$1,116.75	$1,116.80