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	$215.76	12.225%	$242.1367	$242.14	$242.15	$242.10
Purchase #2	$180.32	11.211%	$200.5357	$200.54	$200.55	$200.50
Purchase #3	$10.33	7.759%	$11.1315	$11.13	$11.15	$11.10
Purchase #4	$11.92	9.129%	$13.0082	$13.01	$13.00	$13.00
Purchase #5	$190.55	7.517%	$204.8736	$204.87	$204.85	$204.90
Purchase #6	$25.54	10.759%	$28.2878	$28.29	$28.30	$28.30
Purchase #7	$59.25	5.725%	$62.6421	$62.64	$62.65	$62.60
7 purchase totals =	$693.67		$762.6156	$762.62	$762.65	$762.50