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	$217.89	10.506%	$240.7815	$240.78	$240.80	$240.80
Purchase #2	$76.91	5.448%	$81.1001	$81.10	$81.10	$81.10
Purchase #3	$13.82	7.337%	$14.834	$14.83	$14.85	$14.80
Purchase #4	$195.34	10.137%	$215.1416	$215.14	$215.15	$215.10
Purchase #5	$212.85	3.786%	$220.9085	$220.91	$220.90	$220.90
Purchase #6	$10.50	12.603%	$11.8233	$11.82	$11.80	$11.80
Purchase #7	$92.44	9.149%	$100.8973	$100.90	$100.90	$100.90
7 purchase totals =	$819.75		$885.4863	$885.48	$885.50	$885.40