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	$209.98	4.509%	$219.448	$219.45	$219.45	$219.40
Purchase #2	$31.43	13.663%	$35.7243	$35.72	$35.70	$35.70
Purchase #3	$116.64	12.181%	$130.8479	$130.85	$130.85	$130.80
Purchase #4	$141.91	7.436%	$152.4624	$152.46	$152.45	$152.50
Purchase #5	$62.91	8.106%	$68.0095	$68.01	$68.00	$68.00
Purchase #6	$13.54	11.471%	$15.0932	$15.09	$15.10	$15.10
Purchase #7	$219.90	13.417%	$249.404	$249.40	$249.40	$249.40
7 purchase totals =	$796.31		$870.9893	$870.98	$870.95	$870.90