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	$13.43	4.450%	$14.0276	$14.03	$14.05	$14.00
Purchase #2	$37.78	13.417%	$42.8489	$42.85	$42.85	$42.80
Purchase #3	$217.94	4.709%	$228.2028	$228.20	$228.20	$228.20
Purchase #4	$15.91	10.444%	$17.5716	$17.57	$17.55	$17.60
Purchase #5	$92.65	12.592%	$104.3165	$104.32	$104.30	$104.30
Purchase #6	$87.50	3.870%	$90.8863	$90.89	$90.90	$90.90
Purchase #7	$85.37	10.681%	$94.4884	$94.49	$94.50	$94.50
7 purchase totals =	$550.58		$592.3421	$592.35	$592.35	$592.30