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	$41.35	5.389%	$43.5784	$43.58	$43.60	$43.60
Purchase #2	$102.80	8.562%	$111.6017	$111.60	$111.60	$111.60
Purchase #3	$7.58	4.861%	$7.9485	$7.95	$7.95	$7.90
Purchase #4	$119.73	12.557%	$134.7645	$134.76	$134.75	$134.80
Purchase #5	$127.66	7.497%	$137.2307	$137.23	$137.25	$137.20
Purchase #6	$36.95	10.494%	$40.8275	$40.83	$40.85	$40.80
Purchase #7	$179.30	7.582%	$192.8945	$192.89	$192.90	$192.90
7 purchase totals =	$615.37		$668.8458	$668.84	$668.90	$668.80