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	$29.68	8.811%	$32.2951	$32.30	$32.30	$32.30
Purchase #2	$116.38	13.247%	$131.7969	$131.80	$131.80	$131.80
Purchase #3	$151.86	8.593%	$164.9093	$164.91	$164.90	$164.90
Purchase #4	$81.75	4.858%	$85.7214	$85.72	$85.70	$85.70
Purchase #5	$88.63	8.156%	$95.8587	$95.86	$95.85	$95.90
Purchase #6	$56.40	7.141%	$60.4275	$60.43	$60.45	$60.40
Purchase #7	$203.79	4.755%	$213.4802	$213.48	$213.50	$213.50
7 purchase totals =	$728.49		$784.4891	$784.50	$784.50	$784.50