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	$143.85	4.857%	$150.8368	$150.84	$150.85	$150.80
Purchase #2	$31.93	11.111%	$35.4777	$35.48	$35.50	$35.50
Purchase #3	$78.80	10.334%	$86.9432	$86.94	$86.95	$86.90
Purchase #4	$182.65	7.502%	$196.3524	$196.35	$196.35	$196.40
Purchase #5	$43.80	4.275%	$45.6725	$45.67	$45.65	$45.70
Purchase #6	$218.54	12.488%	$245.8313	$245.83	$245.85	$245.80
Purchase #7	$117.98	11.724%	$131.812	$131.81	$131.80	$131.80
7 purchase totals =	$817.55		$892.9259	$892.92	$892.95	$892.90