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	$191.82	11.222%	$213.346	$213.35	$213.35	$213.30
Purchase #2	$79.89	4.491%	$83.4779	$83.48	$83.50	$83.50
Purchase #3	$31.66	11.846%	$35.4104	$35.41	$35.40	$35.40
Purchase #4	$128.88	5.269%	$135.6707	$135.67	$135.65	$135.70
Purchase #5	$136.38	6.778%	$145.6238	$145.62	$145.60	$145.60
Purchase #6	$207.75	12.271%	$233.243	$233.24	$233.25	$233.20
Purchase #7	$125.77	4.776%	$131.7768	$131.78	$131.80	$131.80
7 purchase totals =	$902.15		$978.5486	$978.55	$978.55	$978.50