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	$190.93	13.384%	$216.4841	$216.48	$216.50	$216.50
Purchase #2	$195.79	11.644%	$218.5878	$218.59	$218.60	$218.60
Purchase #3	$109.80	5.484%	$115.8214	$115.82	$115.80	$115.80
Purchase #4	$30.51	7.767%	$32.8797	$32.88	$32.90	$32.90
Purchase #5	$159.66	9.189%	$174.3312	$174.33	$174.35	$174.30
Purchase #6	$211.61	3.260%	$218.5085	$218.51	$218.50	$218.50
Purchase #7	$59.63	13.153%	$67.4731	$67.47	$67.45	$67.50
7 purchase totals =	$957.93		$1,044.0858	$1,044.08	$1,044.10	$1,044.10