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	$167.49	13.809%	$190.6187	$190.62	$190.60	$190.60
Purchase #2	$248.92	5.263%	$262.0207	$262.02	$262.00	$262.00
Purchase #3	$198.95	4.709%	$208.3186	$208.32	$208.30	$208.30
Purchase #4	$64.53	11.350%	$71.8542	$71.85	$71.85	$71.90
Purchase #5	$64.70	4.485%	$67.6018	$67.60	$67.60	$67.60
Purchase #6	$13.88	11.116%	$15.4229	$15.42	$15.40	$15.40
Purchase #7	$134.90	12.729%	$152.0714	$152.07	$152.05	$152.10
7 purchase totals =	$893.37		$967.9083	$967.90	$967.80	$967.90