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	$248.52	13.170%	$281.2501	$281.25	$281.25	$281.30
Purchase #2	$43.96	8.294%	$47.606	$47.61	$47.60	$47.60
Purchase #3	$216.51	13.763%	$246.3083	$246.31	$246.30	$246.30
Purchase #4	$46.56	13.481%	$52.8368	$52.84	$52.85	$52.80
Purchase #5	$50.57	7.317%	$54.2702	$54.27	$54.25	$54.30
Purchase #6	$223.99	13.331%	$253.8501	$253.85	$253.85	$253.90
Purchase #7	$185.67	10.687%	$205.5126	$205.51	$205.50	$205.50
7 purchase totals =	$1,015.78		$1,141.6341	$1,141.64	$1,141.60	$1,141.70