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	$88.96	6.516%	$94.7566	$94.76	$94.75	$94.80
Purchase #2	$63.79	4.190%	$66.4628	$66.46	$66.45	$66.50
Purchase #3	$174.90	7.276%	$187.6257	$187.63	$187.65	$187.60
Purchase #4	$37.73	11.385%	$42.0256	$42.03	$42.05	$42.00
Purchase #5	$117.50	9.554%	$128.726	$128.73	$128.75	$128.70
Purchase #6	$167.39	9.298%	$182.9539	$182.95	$182.95	$183.00
Purchase #7	$152.31	10.643%	$168.5204	$168.52	$168.50	$168.50
7 purchase totals =	$802.58		$871.0710	$871.08	$871.10	$871.10