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	$131.49	7.457%	$141.2952	$141.30	$141.30	$141.30
Purchase #2	$26.68	5.227%	$28.0746	$28.07	$28.05	$28.10
Purchase #3	$46.82	10.327%	$51.6551	$51.66	$51.65	$51.70
Purchase #4	$36.84	4.509%	$38.5011	$38.50	$38.50	$38.50
Purchase #5	$205.35	8.308%	$222.4105	$222.41	$222.40	$222.40
Purchase #6	$200.63	5.133%	$210.9283	$210.93	$210.95	$210.90
Purchase #7	$93.98	10.315%	$103.674	$103.67	$103.65	$103.70
7 purchase totals =	$741.79		$796.5388	$796.54	$796.50	$796.60