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	$78.52	7.492%	$84.4027	$84.40	$84.40	$84.40
Purchase #2	$40.43	5.140%	$42.5081	$42.51	$42.50	$42.50
Purchase #3	$162.46	4.427%	$169.6521	$169.65	$169.65	$169.70
Purchase #4	$248.90	13.652%	$282.8798	$282.88	$282.90	$282.90
Purchase #5	$237.71	6.466%	$253.0803	$253.08	$253.10	$253.10
Purchase #6	$108.97	3.383%	$112.6565	$112.66	$112.65	$112.70
Purchase #7	$54.86	4.430%	$57.2903	$57.29	$57.30	$57.30
7 purchase totals =	$931.85		$1,002.4698	$1,002.47	$1,002.50	$1,002.60