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	$35.87	4.261%	$37.3984	$37.40	$37.40	$37.40
Purchase #2	$113.86	4.386%	$118.8539	$118.85	$118.85	$118.90
Purchase #3	$26.86	3.811%	$27.8836	$27.88	$27.90	$27.90
Purchase #4	$145.27	13.486%	$164.8611	$164.86	$164.85	$164.90
Purchase #5	$87.86	12.395%	$98.7502	$98.75	$98.75	$98.80
Purchase #6	$155.78	6.247%	$165.5116	$165.51	$165.50	$165.50
Purchase #7	$97.85	4.160%	$101.9206	$101.92	$101.90	$101.90
7 purchase totals =	$663.35		$715.1794	$715.17	$715.15	$715.30