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	$37.27	11.617%	$41.5997	$41.60	$41.60	$41.60
Purchase #2	$159.99	5.323%	$168.5063	$168.51	$168.50	$168.50
Purchase #3	$48.86	11.223%	$54.3436	$54.34	$54.35	$54.30
Purchase #4	$153.46	9.665%	$168.2919	$168.29	$168.30	$168.30
Purchase #5	$31.26	7.401%	$33.5736	$33.57	$33.55	$33.60
Purchase #6	$95.76	9.221%	$104.59	$104.59	$104.60	$104.60
Purchase #7	$228.46	13.517%	$259.3409	$259.34	$259.35	$259.30
7 purchase totals =	$755.06		$830.2460	$830.24	$830.25	$830.20