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	$42.91	6.267%	$45.5992	$45.60	$45.60	$45.60
Purchase #2	$167.86	11.589%	$187.3133	$187.31	$187.30	$187.30
Purchase #3	$133.76	5.787%	$141.5007	$141.50	$141.50	$141.50
Purchase #4	$183.58	7.273%	$196.9318	$196.93	$196.95	$196.90
Purchase #5	$218.80	12.619%	$246.4104	$246.41	$246.40	$246.40
Purchase #6	$121.79	12.547%	$137.071	$137.07	$137.05	$137.10
Purchase #7	$69.67	12.129%	$78.1203	$78.12	$78.10	$78.10
7 purchase totals =	$938.37		$1,032.9467	$1,032.94	$1,032.90	$1,032.90