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	$181.48	10.249%	$200.0799	$200.08	$200.10	$200.10
Purchase #2	$236.82	8.418%	$256.7555	$256.76	$256.75	$256.80
Purchase #3	$56.99	3.758%	$59.1317	$59.13	$59.15	$59.10
Purchase #4	$38.83	5.770%	$41.0705	$41.07	$41.05	$41.10
Purchase #5	$188.74	11.285%	$210.0393	$210.04	$210.05	$210.00
Purchase #6	$249.89	3.268%	$258.0564	$258.06	$258.05	$258.10
Purchase #7	$132.98	8.314%	$144.036	$144.04	$144.05	$144.00
7 purchase totals =	$1,085.73		$1,169.1693	$1,169.18	$1,169.20	$1,169.20