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	$32.57	8.577%	$35.3635	$35.36	$35.35	$35.40
Purchase #2	$10.50	6.456%	$11.1779	$11.18	$11.20	$11.20
Purchase #3	$218.61	11.108%	$242.8932	$242.89	$242.90	$242.90
Purchase #4	$69.52	4.804%	$72.8597	$72.86	$72.85	$72.90
Purchase #5	$150.88	6.358%	$160.473	$160.47	$160.45	$160.50
Purchase #6	$102.74	11.361%	$114.4123	$114.41	$114.40	$114.40
Purchase #7	$131.84	7.797%	$142.1196	$142.12	$142.10	$142.10
7 purchase totals =	$716.66		$779.2992	$779.29	$779.25	$779.40