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	$228.89	3.350%	$236.5578	$236.56	$236.55	$236.60
Purchase #2	$118.58	4.183%	$123.5402	$123.54	$123.55	$123.50
Purchase #3	$245.82	6.373%	$261.4861	$261.49	$261.50	$261.50
Purchase #4	$114.60	5.837%	$121.2892	$121.29	$121.30	$121.30
Purchase #5	$142.99	3.458%	$147.9346	$147.93	$147.95	$147.90
Purchase #6	$73.66	13.504%	$83.607	$83.61	$83.60	$83.60
Purchase #7	$78.89	8.454%	$85.5594	$85.56	$85.55	$85.60
7 purchase totals =	$1,003.43		$1,059.9743	$1,059.98	$1,060.00	$1,060.00