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	$167.73	10.489%	$185.3232	$185.32	$185.30	$185.30
Purchase #2	$210.79	6.778%	$225.0773	$225.08	$225.10	$225.10
Purchase #3	$223.78	13.663%	$254.3551	$254.36	$254.35	$254.40
Purchase #4	$48.92	9.371%	$53.5043	$53.50	$53.50	$53.50
Purchase #5	$10.88	3.695%	$11.282	$11.28	$11.30	$11.30
Purchase #6	$102.71	9.252%	$112.2127	$112.21	$112.20	$112.20
Purchase #7	$175.83	8.239%	$190.3166	$190.32	$190.30	$190.30
7 purchase totals =	$940.64		$1,032.0712	$1,032.07	$1,032.05	$1,032.10