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	$216.50	8.383%	$234.6492	$234.65	$234.65	$234.60
Purchase #2	$240.33	10.272%	$265.0167	$265.02	$265.00	$265.00
Purchase #3	$22.30	12.486%	$25.0844	$25.08	$25.10	$25.10
Purchase #4	$80.60	11.492%	$89.8626	$89.86	$89.85	$89.90
Purchase #5	$172.43	13.736%	$196.115	$196.12	$196.10	$196.10
Purchase #6	$114.39	4.153%	$119.1406	$119.14	$119.15	$119.10
Purchase #7	$156.93	4.170%	$163.474	$163.47	$163.45	$163.50
7 purchase totals =	$1,003.48		$1,093.3425	$1,093.34	$1,093.30	$1,093.30