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	$91.85	8.679%	$99.8217	$99.82	$99.80	$99.80
Purchase #2	$96.47	13.596%	$109.5861	$109.59	$109.60	$109.60
Purchase #3	$217.98	3.683%	$226.0082	$226.01	$226.00	$226.00
Purchase #4	$55.84	11.405%	$62.2086	$62.21	$62.20	$62.20
Purchase #5	$13.33	6.384%	$14.181	$14.18	$14.20	$14.20
Purchase #6	$197.83	13.232%	$224.0069	$224.01	$224.00	$224.00
Purchase #7	$75.31	4.542%	$78.7306	$78.73	$78.75	$78.70
7 purchase totals =	$748.61		$814.5431	$814.55	$814.55	$814.50