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	$56.82	3.131%	$58.599	$58.60	$58.60	$58.60
Purchase #2	$61.52	10.346%	$67.8849	$67.88	$67.90	$67.90
Purchase #3	$73.25	7.691%	$78.8837	$78.88	$78.90	$78.90
Purchase #4	$121.45	8.332%	$131.5692	$131.57	$131.55	$131.60
Purchase #5	$208.92	13.562%	$237.2537	$237.25	$237.25	$237.30
Purchase #6	$43.96	11.333%	$48.942	$48.94	$48.95	$48.90
Purchase #7	$148.67	9.568%	$162.8947	$162.89	$162.90	$162.90
7 purchase totals =	$714.59		$786.0272	$786.01	$786.05	$786.10