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	$31.52	5.757%	$33.3346	$33.33	$33.35	$33.30
Purchase #2	$70.85	9.362%	$77.483	$77.48	$77.50	$77.50
Purchase #3	$79.67	11.466%	$88.805	$88.81	$88.80	$88.80
Purchase #4	$86.61	5.693%	$91.5407	$91.54	$91.55	$91.50
Purchase #5	$96.50	13.318%	$109.3519	$109.35	$109.35	$109.40
Purchase #6	$33.77	3.531%	$34.9624	$34.96	$34.95	$35.00
Purchase #7	$154.44	10.575%	$170.772	$170.77	$170.75	$170.80
7 purchase totals =	$553.36		$606.2496	$606.24	$606.25	$606.30