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	$43.89	4.585%	$45.9024	$45.90	$45.90	$45.90
Purchase #2	$113.34	13.863%	$129.0523	$129.05	$129.05	$129.10
Purchase #3	$59.55	4.138%	$62.0142	$62.01	$62.00	$62.00
Purchase #4	$213.62	4.508%	$223.25	$223.25	$223.25	$223.30
Purchase #5	$102.30	7.137%	$109.6012	$109.60	$109.60	$109.60
Purchase #6	$240.52	13.331%	$272.5837	$272.58	$272.60	$272.60
Purchase #7	$243.82	13.835%	$277.5525	$277.55	$277.55	$277.60
7 purchase totals =	$1,017.04		$1,119.9563	$1,119.94	$1,119.95	$1,120.10