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	$195.27	12.509%	$219.6963	$219.70	$219.70	$219.70
Purchase #2	$207.99	8.474%	$225.6151	$225.62	$225.60	$225.60
Purchase #3	$172.87	10.825%	$191.5832	$191.58	$191.60	$191.60
Purchase #4	$164.33	11.301%	$182.9009	$182.90	$182.90	$182.90
Purchase #5	$32.81	11.477%	$36.5756	$36.58	$36.60	$36.60
Purchase #6	$82.38	3.375%	$85.1603	$85.16	$85.15	$85.20
Purchase #7	$233.89	13.435%	$265.3131	$265.31	$265.30	$265.30
7 purchase totals =	$1,089.54		$1,206.8445	$1,206.85	$1,206.85	$1,206.90