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	$96.90	13.363%	$109.8487	$109.85	$109.85	$109.80
Purchase #2	$31.29	5.508%	$33.0135	$33.01	$33.00	$33.00
Purchase #3	$63.32	8.121%	$68.4622	$68.46	$68.45	$68.50
Purchase #4	$128.40	6.307%	$136.4982	$136.50	$136.50	$136.50
Purchase #5	$75.29	10.158%	$82.938	$82.94	$82.95	$82.90
Purchase #6	$247.45	4.364%	$258.2487	$258.25	$258.25	$258.20
Purchase #7	$85.39	12.386%	$95.9664	$95.97	$95.95	$96.00
7 purchase totals =	$728.04		$784.9757	$784.98	$784.95	$784.90