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	$60.69	3.263%	$62.6703	$62.67	$62.65	$62.70
Purchase #2	$188.55	4.427%	$196.8971	$196.90	$196.90	$196.90
Purchase #3	$33.54	10.348%	$37.0107	$37.01	$37.00	$37.00
Purchase #4	$5.67	3.535%	$5.8704	$5.87	$5.85	$5.90
Purchase #5	$102.77	13.368%	$116.5083	$116.51	$116.50	$116.50
Purchase #6	$172.73	11.155%	$191.998	$192.00	$192.00	$192.00
Purchase #7	$40.81	6.822%	$43.5941	$43.59	$43.60	$43.60
7 purchase totals =	$604.76		$654.5489	$654.55	$654.50	$654.60