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	$130.52	5.584%	$137.8082	$137.81	$137.80	$137.80
Purchase #2	$74.63	5.290%	$78.5779	$78.58	$78.60	$78.60
Purchase #3	$179.88	12.787%	$202.8813	$202.88	$202.90	$202.90
Purchase #4	$33.47	6.305%	$35.5803	$35.58	$35.60	$35.60
Purchase #5	$66.91	8.801%	$72.7987	$72.80	$72.80	$72.80
Purchase #6	$182.49	7.116%	$195.476	$195.48	$195.50	$195.50
Purchase #7	$16.80	8.862%	$18.2888	$18.29	$18.30	$18.30
7 purchase totals =	$684.70		$741.4112	$741.42	$741.50	$741.50