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	$100.47	3.355%	$103.8408	$103.84	$103.85	$103.80
Purchase #2	$194.57	11.314%	$216.5836	$216.58	$216.60	$216.60
Purchase #3	$27.82	11.820%	$31.1083	$31.11	$31.10	$31.10
Purchase #4	$63.60	6.237%	$67.5667	$67.57	$67.55	$67.60
Purchase #5	$92.46	10.785%	$102.4318	$102.43	$102.45	$102.40
Purchase #6	$104.47	4.294%	$108.9559	$108.96	$108.95	$109.00
Purchase #7	$78.96	9.405%	$86.3862	$86.39	$86.40	$86.40
7 purchase totals =	$662.35		$716.8733	$716.88	$716.90	$716.90