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	$203.27	7.689%	$218.8994	$218.90	$218.90	$218.90
Purchase #2	$85.35	12.255%	$95.8096	$95.81	$95.80	$95.80
Purchase #3	$78.95	6.193%	$83.8394	$83.84	$83.85	$83.80
Purchase #4	$230.61	5.516%	$243.3304	$243.33	$243.35	$243.30
Purchase #5	$116.53	12.445%	$131.0322	$131.03	$131.05	$131.00
Purchase #6	$25.72	4.554%	$26.8913	$26.89	$26.90	$26.90
Purchase #7	$238.74	7.342%	$256.2683	$256.27	$256.25	$256.30
7 purchase totals =	$979.17		$1,056.0706	$1,056.07	$1,056.10	$1,056.00