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	$228.38	5.288%	$240.4567	$240.46	$240.45	$240.50
Purchase #2	$106.31	7.549%	$114.3353	$114.34	$114.35	$114.30
Purchase #3	$85.48	5.701%	$90.3532	$90.35	$90.35	$90.40
Purchase #4	$123.76	10.621%	$136.9045	$136.90	$136.90	$136.90
Purchase #5	$37.77	13.483%	$42.8625	$42.86	$42.85	$42.90
Purchase #6	$201.72	11.115%	$224.1412	$224.14	$224.15	$224.10
Purchase #7	$220.51	7.372%	$236.766	$236.77	$236.75	$236.80
7 purchase totals =	$1,003.93		$1,085.8194	$1,085.82	$1,085.80	$1,085.90