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	$37.83	6.409%	$40.2545	$40.25	$40.25	$40.30
Purchase #2	$215.90	13.130%	$244.2477	$244.25	$244.25	$244.20
Purchase #3	$191.72	3.746%	$198.9018	$198.90	$198.90	$198.90
Purchase #4	$43.65	7.527%	$46.9355	$46.94	$46.95	$46.90
Purchase #5	$126.43	12.494%	$142.2262	$142.23	$142.25	$142.20
Purchase #6	$179.84	11.468%	$200.4641	$200.46	$200.45	$200.50
Purchase #7	$246.98	11.562%	$275.5358	$275.54	$275.55	$275.50
7 purchase totals =	$1,042.35		$1,148.5656	$1,148.57	$1,148.60	$1,148.50