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	$47.89	11.535%	$53.4141	$53.41	$53.40	$53.40
Purchase #2	$11.55	10.462%	$12.7584	$12.76	$12.75	$12.80
Purchase #3	$173.64	6.818%	$185.4788	$185.48	$185.50	$185.50
Purchase #4	$211.46	7.409%	$227.1271	$227.13	$227.15	$227.10
Purchase #5	$51.38	13.804%	$58.4725	$58.47	$58.45	$58.50
Purchase #6	$161.60	11.835%	$180.7254	$180.73	$180.75	$180.70
Purchase #7	$63.92	4.628%	$66.8782	$66.88	$66.90	$66.90
7 purchase totals =	$721.44		$784.8545	$784.86	$784.90	$784.90