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	$201.48	8.401%	$218.4063	$218.41	$218.40	$218.40
Purchase #2	$35.71	3.309%	$36.8916	$36.89	$36.90	$36.90
Purchase #3	$186.95	12.582%	$210.472	$210.47	$210.45	$210.50
Purchase #4	$184.82	13.544%	$209.852	$209.85	$209.85	$209.90
Purchase #5	$176.95	13.206%	$200.318	$200.32	$200.30	$200.30
Purchase #6	$59.43	11.326%	$66.161	$66.16	$66.15	$66.20
Purchase #7	$181.37	5.757%	$191.8115	$191.81	$191.80	$191.80
7 purchase totals =	$1,026.71		$1,133.9124	$1,133.91	$1,133.85	$1,134.00