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	$146.75	5.397%	$154.6701	$154.67	$154.65	$154.70
Purchase #2	$169.34	10.404%	$186.9581	$186.96	$186.95	$187.00
Purchase #3	$187.47	11.443%	$208.9222	$208.92	$208.90	$208.90
Purchase #4	$176.58	13.764%	$200.8845	$200.88	$200.90	$200.90
Purchase #5	$34.44	4.235%	$35.8985	$35.90	$35.90	$35.90
Purchase #6	$171.50	10.811%	$190.0409	$190.04	$190.05	$190.00
Purchase #7	$56.55	5.373%	$59.5884	$59.59	$59.60	$59.60
7 purchase totals =	$942.63		$1,036.9627	$1,036.96	$1,036.95	$1,037.00