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	$70.34	8.564%	$76.3639	$76.36	$76.35	$76.40
Purchase #2	$226.82	5.627%	$239.5832	$239.58	$239.60	$239.60
Purchase #3	$206.75	8.365%	$224.0446	$224.04	$224.05	$224.00
Purchase #4	$12.84	8.592%	$13.9432	$13.94	$13.95	$13.90
Purchase #5	$75.83	3.503%	$78.4863	$78.49	$78.50	$78.50
Purchase #6	$184.48	3.457%	$190.8575	$190.86	$190.85	$190.90
Purchase #7	$167.56	7.766%	$180.5727	$180.57	$180.55	$180.60
7 purchase totals =	$944.62		$1,003.8514	$1,003.84	$1,003.85	$1,003.90