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	$68.56	4.151%	$71.4059	$71.41	$71.40	$71.40
Purchase #2	$168.65	13.737%	$191.8175	$191.82	$191.80	$191.80
Purchase #3	$27.33	8.255%	$29.5861	$29.59	$29.60	$29.60
Purchase #4	$222.89	6.577%	$237.5495	$237.55	$237.55	$237.50
Purchase #5	$249.55	12.800%	$281.4924	$281.49	$281.50	$281.50
Purchase #6	$31.72	10.374%	$35.0106	$35.01	$35.00	$35.00
Purchase #7	$129.67	8.435%	$140.6077	$140.61	$140.60	$140.60
7 purchase totals =	$898.37		$987.4697	$987.48	$987.45	$987.40