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	$60.84	8.117%	$65.7784	$65.78	$65.80	$65.80
Purchase #2	$210.28	6.765%	$224.5054	$224.51	$224.50	$224.50
Purchase #3	$186.88	11.756%	$208.8496	$208.85	$208.85	$208.80
Purchase #4	$179.90	3.688%	$186.5347	$186.53	$186.55	$186.50
Purchase #5	$224.33	12.211%	$251.7229	$251.72	$251.70	$251.70
Purchase #6	$78.82	12.446%	$88.6299	$88.63	$88.65	$88.60
Purchase #7	$35.64	12.443%	$40.0747	$40.07	$40.05	$40.10
7 purchase totals =	$976.69		$1,066.0956	$1,066.09	$1,066.10	$1,066.00