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	$163.33	10.120%	$179.859	$179.86	$179.85	$179.90
Purchase #2	$104.99	4.325%	$109.5308	$109.53	$109.55	$109.50
Purchase #3	$157.67	7.137%	$168.9229	$168.92	$168.90	$168.90
Purchase #4	$191.87	4.649%	$200.79	$200.79	$200.80	$200.80
Purchase #5	$90.77	8.622%	$98.5962	$98.60	$98.60	$98.60
Purchase #6	$223.52	7.132%	$239.4614	$239.46	$239.45	$239.50
Purchase #7	$108.34	6.765%	$115.6692	$115.67	$115.65	$115.70
7 purchase totals =	$1,040.49		$1,112.8295	$1,112.83	$1,112.80	$1,112.90