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	$43.62	4.283%	$45.4882	$45.49	$45.50	$45.50
Purchase #2	$51.57	9.220%	$56.3248	$56.32	$56.30	$56.30
Purchase #3	$224.29	7.644%	$241.4347	$241.43	$241.45	$241.40
Purchase #4	$80.97	10.293%	$89.3042	$89.30	$89.30	$89.30
Purchase #5	$158.55	11.588%	$176.9228	$176.92	$176.90	$176.90
Purchase #6	$32.30	10.310%	$35.6301	$35.63	$35.65	$35.60
Purchase #7	$192.70	11.711%	$215.2671	$215.27	$215.25	$215.30
7 purchase totals =	$784.00		$860.3719	$860.36	$860.35	$860.30