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	$196.66	10.524%	$217.3565	$217.36	$217.35	$217.40
Purchase #2	$35.53	13.132%	$40.1958	$40.20	$40.20	$40.20
Purchase #3	$86.61	12.343%	$97.3003	$97.30	$97.30	$97.30
Purchase #4	$38.99	8.377%	$42.2562	$42.26	$42.25	$42.30
Purchase #5	$86.90	6.255%	$92.3356	$92.34	$92.35	$92.30
Purchase #6	$123.45	6.456%	$131.4199	$131.42	$131.40	$131.40
Purchase #7	$30.61	6.181%	$32.502	$32.50	$32.50	$32.50
7 purchase totals =	$598.75		$653.3663	$653.38	$653.35	$653.40