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	$56.65	4.828%	$59.3851	$59.39	$59.40	$59.40
Purchase #2	$67.49	8.710%	$73.3684	$73.37	$73.35	$73.40
Purchase #3	$88.58	7.277%	$95.026	$95.03	$95.05	$95.00
Purchase #4	$33.45	5.411%	$35.26	$35.26	$35.25	$35.30
Purchase #5	$138.28	10.574%	$152.9017	$152.90	$152.90	$152.90
Purchase #6	$81.74	6.811%	$87.3073	$87.31	$87.30	$87.30
Purchase #7	$164.46	12.424%	$184.8925	$184.89	$184.90	$184.90
7 purchase totals =	$630.65		$688.1410	$688.15	$688.15	$688.20