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	$203.81	11.169%	$226.5735	$226.57	$226.55	$226.60
Purchase #2	$79.73	13.159%	$90.2217	$90.22	$90.20	$90.20
Purchase #3	$112.58	9.372%	$123.131	$123.13	$123.15	$123.10
Purchase #4	$73.30	6.728%	$78.2316	$78.23	$78.25	$78.20
Purchase #5	$21.59	7.676%	$23.2472	$23.25	$23.25	$23.20
Purchase #6	$233.56	13.184%	$264.3526	$264.35	$264.35	$264.40
Purchase #7	$22.36	11.358%	$24.8996	$24.90	$24.90	$24.90
7 purchase totals =	$746.93		$830.6572	$830.65	$830.65	$830.60