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	$109.70	3.322%	$113.3442	$113.34	$113.35	$113.30
Purchase #2	$153.65	9.668%	$168.5049	$168.50	$168.50	$168.50
Purchase #3	$136.57	3.862%	$141.8443	$141.84	$141.85	$141.80
Purchase #4	$93.96	3.405%	$97.1593	$97.16	$97.15	$97.20
Purchase #5	$144.35	12.283%	$162.0805	$162.08	$162.10	$162.10
Purchase #6	$99.41	11.758%	$111.0986	$111.10	$111.10	$111.10
Purchase #7	$208.92	4.619%	$218.57	$218.57	$218.55	$218.60
7 purchase totals =	$946.56		$1,012.6018	$1,012.59	$1,012.60	$1,012.60