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	$144.26	11.519%	$160.8773	$160.88	$160.90	$160.90
Purchase #2	$24.71	3.273%	$25.5188	$25.52	$25.50	$25.50
Purchase #3	$172.32	10.586%	$190.5618	$190.56	$190.55	$190.60
Purchase #4	$108.88	3.679%	$112.8857	$112.89	$112.90	$112.90
Purchase #5	$34.67	3.489%	$35.8796	$35.88	$35.90	$35.90
Purchase #6	$125.32	8.444%	$135.902	$135.90	$135.90	$135.90
Purchase #7	$74.73	5.144%	$78.5741	$78.57	$78.55	$78.60
7 purchase totals =	$684.89		$740.1993	$740.20	$740.20	$740.30