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	$167.60	12.544%	$188.6237	$188.62	$188.60	$188.60
Purchase #2	$92.48	8.742%	$100.5646	$100.56	$100.55	$100.60
Purchase #3	$73.82	10.271%	$81.4021	$81.40	$81.40	$81.40
Purchase #4	$145.86	11.834%	$163.1211	$163.12	$163.10	$163.10
Purchase #5	$83.82	7.602%	$90.192	$90.19	$90.20	$90.20
Purchase #6	$166.31	7.291%	$178.4357	$178.44	$178.45	$178.40
Purchase #7	$134.57	3.647%	$139.4778	$139.48	$139.50	$139.50
7 purchase totals =	$864.46		$941.8170	$941.81	$941.80	$941.80