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	$190.41	13.742%	$216.5761	$216.58	$216.60	$216.60
Purchase #2	$207.39	7.528%	$223.0023	$223.00	$223.00	$223.00
Purchase #3	$123.50	11.223%	$137.3604	$137.36	$137.35	$137.40
Purchase #4	$78.81	10.752%	$87.2837	$87.28	$87.30	$87.30
Purchase #5	$240.82	5.540%	$254.1614	$254.16	$254.15	$254.20
Purchase #6	$89.38	5.276%	$94.0957	$94.10	$94.10	$94.10
Purchase #7	$187.53	4.819%	$196.5671	$196.57	$196.55	$196.60
7 purchase totals =	$1,117.84		$1,209.0467	$1,209.05	$1,209.05	$1,209.20