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	$84.92	8.851%	$92.4363	$92.44	$92.45	$92.40
Purchase #2	$109.37	3.714%	$113.432	$113.43	$113.45	$113.40
Purchase #3	$175.37	8.127%	$189.6223	$189.62	$189.60	$189.60
Purchase #4	$123.50	3.830%	$128.2301	$128.23	$128.25	$128.20
Purchase #5	$67.28	9.184%	$73.459	$73.46	$73.45	$73.50
Purchase #6	$166.50	8.113%	$180.0081	$180.01	$180.00	$180.00
Purchase #7	$90.63	10.617%	$100.2522	$100.25	$100.25	$100.30
7 purchase totals =	$817.57		$877.4400	$877.44	$877.45	$877.40