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	$144.31	11.808%	$161.3501	$161.35	$161.35	$161.40
Purchase #2	$243.76	11.212%	$271.0904	$271.09	$271.10	$271.10
Purchase #3	$215.83	3.254%	$222.8531	$222.85	$222.85	$222.90
Purchase #4	$60.91	4.693%	$63.7685	$63.77	$63.75	$63.80
Purchase #5	$56.99	4.170%	$59.3665	$59.37	$59.35	$59.40
Purchase #6	$174.26	3.621%	$180.57	$180.57	$180.55	$180.60
Purchase #7	$133.77	4.529%	$139.8284	$139.83	$139.85	$139.80
7 purchase totals =	$1,029.83		$1,098.8270	$1,098.83	$1,098.80	$1,099.00