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	$56.26	11.568%	$62.7682	$62.77	$62.75	$62.80
Purchase #2	$161.45	11.654%	$180.2654	$180.27	$180.25	$180.30
Purchase #3	$36.31	11.759%	$40.5797	$40.58	$40.60	$40.60
Purchase #4	$31.60	10.544%	$34.9319	$34.93	$34.95	$34.90
Purchase #5	$41.81	8.670%	$45.4349	$45.43	$45.45	$45.40
Purchase #6	$151.90	13.618%	$172.5857	$172.59	$172.60	$172.60
Purchase #7	$110.36	7.581%	$118.7264	$118.73	$118.75	$118.70
7 purchase totals =	$589.69		$655.2922	$655.30	$655.35	$655.30