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	$83.83	11.566%	$93.5258	$93.53	$93.55	$93.50
Purchase #2	$162.82	12.222%	$182.7199	$182.72	$182.70	$182.70
Purchase #3	$76.57	6.614%	$81.6343	$81.63	$81.65	$81.60
Purchase #4	$83.87	7.314%	$90.0043	$90.00	$90.00	$90.00
Purchase #5	$131.39	10.271%	$144.8851	$144.89	$144.90	$144.90
Purchase #6	$20.51	6.843%	$21.9135	$21.91	$21.90	$21.90
Purchase #7	$163.26	3.411%	$168.8288	$168.83	$168.85	$168.80
7 purchase totals =	$722.25		$783.5117	$783.51	$783.55	$783.40