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	$210.72	3.375%	$217.8318	$217.83	$217.85	$217.80
Purchase #2	$158.79	9.145%	$173.3113	$173.31	$173.30	$173.30
Purchase #3	$210.62	12.530%	$237.0107	$237.01	$237.00	$237.00
Purchase #4	$94.41	9.700%	$103.5678	$103.57	$103.55	$103.60
Purchase #5	$217.35	11.706%	$242.793	$242.79	$242.80	$242.80
Purchase #6	$159.80	5.464%	$168.5315	$168.53	$168.55	$168.50
Purchase #7	$38.30	13.486%	$43.4651	$43.47	$43.45	$43.50
7 purchase totals =	$1,089.99		$1,186.5112	$1,186.51	$1,186.50	$1,186.50