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	$52.48	13.584%	$59.6089	$59.61	$59.60	$59.60
Purchase #2	$217.50	13.661%	$247.2127	$247.21	$247.20	$247.20
Purchase #3	$195.61	7.362%	$210.0108	$210.01	$210.00	$210.00
Purchase #4	$57.38	7.729%	$61.8149	$61.81	$61.80	$61.80
Purchase #5	$150.92	9.120%	$164.6839	$164.68	$164.70	$164.70
Purchase #6	$13.72	13.807%	$15.6143	$15.61	$15.60	$15.60
Purchase #7	$93.61	4.539%	$97.859	$97.86	$97.85	$97.90
7 purchase totals =	$781.22		$856.8045	$856.79	$856.75	$856.80