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	$31.35	10.372%	$34.6016	$34.60	$34.60	$34.60
Purchase #2	$126.89	13.559%	$144.095	$144.10	$144.10	$144.10
Purchase #3	$165.34	8.477%	$179.3559	$179.36	$179.35	$179.40
Purchase #4	$38.30	7.290%	$41.0921	$41.09	$41.10	$41.10
Purchase #5	$216.38	11.155%	$240.5172	$240.52	$240.50	$240.50
Purchase #6	$110.30	5.688%	$116.5739	$116.57	$116.55	$116.60
Purchase #7	$5.33	4.821%	$5.587	$5.59	$5.60	$5.60
7 purchase totals =	$693.89		$761.8227	$761.83	$761.80	$761.90