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	$180.47	4.477%	$188.5496	$188.55	$188.55	$188.50
Purchase #2	$124.97	4.732%	$130.8836	$130.88	$130.90	$130.90
Purchase #3	$133.87	6.499%	$142.5702	$142.57	$142.55	$142.60
Purchase #4	$76.25	7.264%	$81.7888	$81.79	$81.80	$81.80
Purchase #5	$244.37	4.142%	$254.4918	$254.49	$254.50	$254.50
Purchase #6	$105.64	10.761%	$117.0079	$117.01	$117.00	$117.00
Purchase #7	$128.84	9.119%	$140.5889	$140.59	$140.60	$140.60
7 purchase totals =	$994.41		$1,055.8808	$1,055.88	$1,055.90	$1,055.90