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	$83.76	3.643%	$86.8114	$86.81	$86.80	$86.80
Purchase #2	$133.57	6.605%	$142.3923	$142.39	$142.40	$142.40
Purchase #3	$249.29	6.516%	$265.5337	$265.53	$265.55	$265.50
Purchase #4	$73.33	13.224%	$83.0272	$83.03	$83.05	$83.00
Purchase #5	$225.81	13.580%	$256.475	$256.48	$256.50	$256.50
Purchase #6	$168.76	10.684%	$186.7903	$186.79	$186.80	$186.80
Purchase #7	$24.74	12.781%	$27.902	$27.90	$27.90	$27.90
7 purchase totals =	$959.26		$1,048.9319	$1,048.93	$1,049.00	$1,048.90