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	$131.59	4.796%	$137.9011	$137.90	$137.90	$137.90
Purchase #2	$109.52	9.150%	$119.5411	$119.54	$119.55	$119.50
Purchase #3	$42.85	7.118%	$45.9001	$45.90	$45.90	$45.90
Purchase #4	$159.85	8.361%	$173.2151	$173.22	$173.20	$173.20
Purchase #5	$31.75	11.763%	$35.4848	$35.48	$35.50	$35.50
Purchase #6	$13.43	4.266%	$14.0029	$14.00	$14.00	$14.00
Purchase #7	$188.41	8.444%	$204.3193	$204.32	$204.30	$204.30
7 purchase totals =	$677.40		$730.3644	$730.36	$730.35	$730.30