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	$33.94	10.385%	$37.4647	$37.46	$37.45	$37.50
Purchase #2	$213.50	12.452%	$240.085	$240.09	$240.10	$240.10
Purchase #3	$51.47	6.176%	$54.6488	$54.65	$54.65	$54.60
Purchase #4	$114.92	6.663%	$122.5771	$122.58	$122.60	$122.60
Purchase #5	$232.48	6.128%	$246.7264	$246.73	$246.75	$246.70
Purchase #6	$90.50	6.488%	$96.3716	$96.37	$96.35	$96.40
Purchase #7	$219.59	8.387%	$238.007	$238.01	$238.00	$238.00
7 purchase totals =	$956.40		$1,035.8806	$1,035.89	$1,035.90	$1,035.90