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	$11.91	10.315%	$13.1385	$13.14	$13.15	$13.10
Purchase #2	$244.89	6.734%	$261.3809	$261.38	$261.40	$261.40
Purchase #3	$167.66	13.190%	$189.7744	$189.77	$189.75	$189.80
Purchase #4	$78.77	4.709%	$82.4793	$82.48	$82.50	$82.50
Purchase #5	$73.49	6.403%	$78.1956	$78.20	$78.20	$78.20
Purchase #6	$247.43	3.661%	$256.4884	$256.49	$256.50	$256.50
Purchase #7	$12.33	13.713%	$14.0208	$14.02	$14.00	$14.00
7 purchase totals =	$836.48		$895.4779	$895.48	$895.50	$895.50