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	$158.79	4.457%	$165.8673	$165.87	$165.85	$165.90
Purchase #2	$223.58	7.473%	$240.2881	$240.29	$240.30	$240.30
Purchase #3	$97.46	4.614%	$101.9568	$101.96	$101.95	$102.00
Purchase #4	$192.52	7.318%	$206.6086	$206.61	$206.60	$206.60
Purchase #5	$32.55	9.270%	$35.5674	$35.57	$35.55	$35.60
Purchase #6	$40.88	7.490%	$43.9419	$43.94	$43.95	$43.90
Purchase #7	$62.81	5.623%	$66.3418	$66.34	$66.35	$66.30
7 purchase totals =	$808.59		$860.5719	$860.58	$860.55	$860.60