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	$198.26	12.675%	$223.3895	$223.39	$223.40	$223.40
Purchase #2	$175.66	3.316%	$181.4849	$181.48	$181.50	$181.50
Purchase #3	$177.31	3.508%	$183.53	$183.53	$183.55	$183.50
Purchase #4	$82.31	6.256%	$87.4593	$87.46	$87.45	$87.50
Purchase #5	$165.73	12.116%	$185.8098	$185.81	$185.80	$185.80
Purchase #6	$76.51	7.286%	$82.0845	$82.08	$82.10	$82.10
Purchase #7	$146.51	10.638%	$162.0957	$162.10	$162.10	$162.10
7 purchase totals =	$1,022.29		$1,105.8537	$1,105.85	$1,105.90	$1,105.90