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	$102.79	8.506%	$111.5333	$111.53	$111.55	$111.50
Purchase #2	$216.61	10.386%	$239.1071	$239.11	$239.10	$239.10
Purchase #3	$219.89	11.461%	$245.0916	$245.09	$245.10	$245.10
Purchase #4	$131.48	4.832%	$137.8331	$137.83	$137.85	$137.80
Purchase #5	$243.83	12.392%	$274.0454	$274.05	$274.05	$274.00
Purchase #6	$45.31	4.544%	$47.3689	$47.37	$47.35	$47.40
Purchase #7	$47.86	10.272%	$52.7762	$52.78	$52.80	$52.80
7 purchase totals =	$1,007.77		$1,107.7556	$1,107.76	$1,107.80	$1,107.70