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	$81.83	12.277%	$91.8763	$91.88	$91.90	$91.90
Purchase #2	$140.90	4.249%	$146.8868	$146.89	$146.90	$146.90
Purchase #3	$28.78	4.849%	$30.1755	$30.18	$30.20	$30.20
Purchase #4	$64.29	6.256%	$68.312	$68.31	$68.30	$68.30
Purchase #5	$138.41	4.138%	$144.1374	$144.14	$144.15	$144.10
Purchase #6	$240.44	13.786%	$273.5871	$273.59	$273.60	$273.60
Purchase #7	$246.58	3.646%	$255.5703	$255.57	$255.55	$255.60
7 purchase totals =	$941.23		$1,010.5454	$1,010.56	$1,010.60	$1,010.60