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	$137.42	5.778%	$145.3601	$145.36	$145.35	$145.40
Purchase #2	$86.67	3.858%	$90.0137	$90.01	$90.00	$90.00
Purchase #3	$209.36	9.519%	$229.289	$229.29	$229.30	$229.30
Purchase #4	$68.62	7.634%	$73.8585	$73.86	$73.85	$73.90
Purchase #5	$164.56	5.289%	$173.2636	$173.26	$173.25	$173.30
Purchase #6	$200.53	10.666%	$221.9185	$221.92	$221.90	$221.90
Purchase #7	$132.39	6.684%	$141.2389	$141.24	$141.25	$141.20
7 purchase totals =	$999.55		$1,074.9423	$1,074.94	$1,074.90	$1,075.00