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	$177.69	7.260%	$190.5903	$190.59	$190.60	$190.60
Purchase #2	$200.74	10.832%	$222.4842	$222.48	$222.50	$222.50
Purchase #3	$78.81	4.270%	$82.1752	$82.18	$82.20	$82.20
Purchase #4	$213.76	12.641%	$240.7814	$240.78	$240.80	$240.80
Purchase #5	$41.54	5.287%	$43.7362	$43.74	$43.75	$43.70
Purchase #6	$203.63	10.848%	$225.7198	$225.72	$225.70	$225.70
Purchase #7	$121.39	3.732%	$125.9203	$125.92	$125.90	$125.90
7 purchase totals =	$1,037.56		$1,131.4074	$1,131.41	$1,131.45	$1,131.40