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	$217.61	11.809%	$243.3076	$243.31	$243.30	$243.30
Purchase #2	$106.87	12.139%	$119.8429	$119.84	$119.85	$119.80
Purchase #3	$109.93	12.272%	$123.4206	$123.42	$123.40	$123.40
Purchase #4	$231.71	6.557%	$246.9032	$246.90	$246.90	$246.90
Purchase #5	$78.30	5.327%	$82.471	$82.47	$82.45	$82.50
Purchase #6	$80.85	11.103%	$89.8268	$89.83	$89.85	$89.80
Purchase #7	$198.87	3.336%	$205.5043	$205.50	$205.50	$205.50
7 purchase totals =	$1,024.14		$1,111.2764	$1,111.27	$1,111.25	$1,111.20