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	$231.57	3.810%	$240.3928	$240.39	$240.40	$240.40
Purchase #2	$162.64	5.438%	$171.4844	$171.48	$171.50	$171.50
Purchase #3	$236.32	11.414%	$263.2936	$263.29	$263.30	$263.30
Purchase #4	$55.35	8.223%	$59.9014	$59.90	$59.90	$59.90
Purchase #5	$223.34	9.491%	$244.5372	$244.54	$244.55	$244.50
Purchase #6	$43.79	11.326%	$48.7497	$48.75	$48.75	$48.70
Purchase #7	$180.48	10.396%	$199.2427	$199.24	$199.25	$199.20
7 purchase totals =	$1,133.49		$1,227.6018	$1,227.59	$1,227.65	$1,227.50