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	$125.40	11.275%	$139.5389	$139.54	$139.55	$139.50
Purchase #2	$70.49	11.342%	$78.485	$78.49	$78.50	$78.50
Purchase #3	$119.66	3.206%	$123.4963	$123.50	$123.50	$123.50
Purchase #4	$248.73	12.626%	$280.1346	$280.13	$280.15	$280.10
Purchase #5	$219.78	4.241%	$229.1009	$229.10	$229.10	$229.10
Purchase #6	$197.78	9.232%	$216.039	$216.04	$216.05	$216.00
Purchase #7	$185.37	4.520%	$193.7487	$193.75	$193.75	$193.70
7 purchase totals =	$1,167.21		$1,260.5434	$1,260.55	$1,260.60	$1,260.40