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	$55.36	13.544%	$62.858	$62.86	$62.85	$62.90
Purchase #2	$91.64	12.276%	$102.8897	$102.89	$102.90	$102.90
Purchase #3	$17.40	9.732%	$19.0934	$19.09	$19.10	$19.10
Purchase #4	$57.47	13.222%	$65.0687	$65.07	$65.05	$65.10
Purchase #5	$206.64	10.796%	$228.9489	$228.95	$228.95	$228.90
Purchase #6	$144.90	13.811%	$164.9121	$164.91	$164.90	$164.90
Purchase #7	$112.30	3.541%	$116.2765	$116.28	$116.30	$116.30
7 purchase totals =	$685.71		$760.0473	$760.05	$760.05	$760.10