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	$41.65	12.867%	$47.0091	$47.01	$47.00	$47.00
Purchase #2	$96.33	13.617%	$109.4473	$109.45	$109.45	$109.40
Purchase #3	$43.56	13.704%	$49.5295	$49.53	$49.55	$49.50
Purchase #4	$125.83	4.683%	$131.7226	$131.72	$131.70	$131.70
Purchase #5	$46.37	12.334%	$52.0893	$52.09	$52.10	$52.10
Purchase #6	$17.65	6.277%	$18.7579	$18.76	$18.75	$18.80
Purchase #7	$141.98	4.843%	$148.8561	$148.86	$148.85	$148.90
7 purchase totals =	$513.37		$557.4118	$557.42	$557.40	$557.40