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	$64.48	4.836%	$67.5983	$67.60	$67.60	$67.60
Purchase #2	$95.91	5.610%	$101.2906	$101.29	$101.30	$101.30
Purchase #3	$152.43	8.683%	$165.6655	$165.67	$165.65	$165.70
Purchase #4	$112.68	5.829%	$119.2481	$119.25	$119.25	$119.20
Purchase #5	$231.65	12.865%	$261.4518	$261.45	$261.45	$261.50
Purchase #6	$97.78	12.354%	$109.8597	$109.86	$109.85	$109.90
Purchase #7	$123.80	6.195%	$131.4694	$131.47	$131.45	$131.50
7 purchase totals =	$878.73		$956.5834	$956.59	$956.55	$956.70