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	$133.71	6.160%	$141.9465	$141.95	$141.95	$141.90
Purchase #2	$153.99	5.130%	$161.8897	$161.89	$161.90	$161.90
Purchase #3	$245.71	5.773%	$259.8948	$259.89	$259.90	$259.90
Purchase #4	$205.69	7.833%	$221.8017	$221.80	$221.80	$221.80
Purchase #5	$189.80	3.321%	$196.1033	$196.10	$196.10	$196.10
Purchase #6	$6.92	8.674%	$7.5202	$7.52	$7.50	$7.50
Purchase #7	$242.62	9.629%	$265.9819	$265.98	$266.00	$266.00
7 purchase totals =	$1,178.44		$1,255.1381	$1,255.13	$1,255.15	$1,255.10