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	$7.41	6.121%	$7.8636	$7.86	$7.85	$7.90
Purchase #2	$228.80	4.384%	$238.8306	$238.83	$238.85	$238.80
Purchase #3	$67.80	9.614%	$74.3183	$74.32	$74.30	$74.30
Purchase #4	$50.72	7.317%	$54.4312	$54.43	$54.45	$54.40
Purchase #5	$76.40	9.249%	$83.4662	$83.47	$83.45	$83.50
Purchase #6	$232.74	13.189%	$263.4361	$263.44	$263.45	$263.40
Purchase #7	$189.72	12.391%	$213.2282	$213.23	$213.25	$213.20
7 purchase totals =	$853.59		$935.5742	$935.58	$935.60	$935.50