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	$169.33	4.128%	$176.3199	$176.32	$176.30	$176.30
Purchase #2	$100.77	11.151%	$112.0069	$112.01	$112.00	$112.00
Purchase #3	$31.70	11.767%	$35.4301	$35.43	$35.45	$35.40
Purchase #4	$160.35	7.214%	$171.9176	$171.92	$171.90	$171.90
Purchase #5	$249.89	13.812%	$284.4048	$284.40	$284.40	$284.40
Purchase #6	$161.39	9.271%	$176.3525	$176.35	$176.35	$176.40
Purchase #7	$107.76	8.108%	$116.4972	$116.50	$116.50	$116.50
7 purchase totals =	$981.19		$1,072.9290	$1,072.93	$1,072.90	$1,072.90