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	$175.34	5.854%	$185.6044	$185.60	$185.60	$185.60
Purchase #2	$201.31	7.696%	$216.8028	$216.80	$216.80	$216.80
Purchase #3	$40.28	6.454%	$42.8797	$42.88	$42.90	$42.90
Purchase #4	$169.41	13.557%	$192.3769	$192.38	$192.40	$192.40
Purchase #5	$111.35	6.495%	$118.5822	$118.58	$118.60	$118.60
Purchase #6	$231.87	12.659%	$261.2224	$261.22	$261.20	$261.20
Purchase #7	$129.89	6.631%	$138.503	$138.50	$138.50	$138.50
7 purchase totals =	$1,059.45		$1,155.9714	$1,155.96	$1,156.00	$1,156.00