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	$231.55	4.840%	$242.757	$242.76	$242.75	$242.80
Purchase #2	$182.77	7.602%	$196.6642	$196.66	$196.65	$196.70
Purchase #3	$149.59	9.796%	$164.2438	$164.24	$164.25	$164.20
Purchase #4	$91.70	8.768%	$99.7403	$99.74	$99.75	$99.70
Purchase #5	$84.87	10.868%	$94.0937	$94.09	$94.10	$94.10
Purchase #6	$131.57	12.774%	$148.3768	$148.38	$148.40	$148.40
Purchase #7	$233.60	3.549%	$241.8905	$241.89	$241.90	$241.90
7 purchase totals =	$1,105.65		$1,187.7663	$1,187.76	$1,187.80	$1,187.80