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	$67.34	4.849%	$70.6053	$70.61	$70.60	$70.60
Purchase #2	$187.82	5.697%	$198.5201	$198.52	$198.50	$198.50
Purchase #3	$126.79	3.600%	$131.3544	$131.35	$131.35	$131.40
Purchase #4	$81.73	4.516%	$85.4209	$85.42	$85.40	$85.40
Purchase #5	$135.81	12.419%	$152.6762	$152.68	$152.70	$152.70
Purchase #6	$242.93	13.368%	$275.4049	$275.40	$275.40	$275.40
Purchase #7	$10.34	6.518%	$11.014	$11.01	$11.00	$11.00
7 purchase totals =	$852.76		$924.9958	$924.99	$924.95	$925.00