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	$223.51	6.850%	$238.8204	$238.82	$238.80	$238.80
Purchase #2	$236.47	3.689%	$245.1934	$245.19	$245.20	$245.20
Purchase #3	$51.55	8.597%	$55.9818	$55.98	$56.00	$56.00
Purchase #4	$157.50	4.525%	$164.6269	$164.63	$164.65	$164.60
Purchase #5	$87.93	3.394%	$90.9143	$90.91	$90.90	$90.90
Purchase #6	$215.85	13.262%	$244.476	$244.48	$244.50	$244.50
Purchase #7	$13.46	12.699%	$15.1693	$15.17	$15.15	$15.20
7 purchase totals =	$986.27		$1,055.1821	$1,055.18	$1,055.20	$1,055.20