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	$218.79	9.201%	$238.9209	$238.92	$238.90	$238.90
Purchase #2	$224.91	7.359%	$241.4611	$241.46	$241.45	$241.50
Purchase #3	$218.59	7.161%	$234.2432	$234.24	$234.25	$234.20
Purchase #4	$135.86	6.389%	$144.5401	$144.54	$144.55	$144.50
Purchase #5	$180.48	5.165%	$189.8018	$189.80	$189.80	$189.80
Purchase #6	$82.84	4.617%	$86.6647	$86.66	$86.65	$86.70
Purchase #7	$103.89	13.508%	$117.9235	$117.92	$117.90	$117.90
7 purchase totals =	$1,165.36		$1,253.5553	$1,253.54	$1,253.50	$1,253.50