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	$95.39	5.174%	$100.3255	$100.33	$100.35	$100.30
Purchase #2	$234.41	10.687%	$259.4614	$259.46	$259.45	$259.50
Purchase #3	$227.95	11.333%	$253.7836	$253.78	$253.80	$253.80
Purchase #4	$230.65	6.866%	$246.4864	$246.49	$246.50	$246.50
Purchase #5	$168.57	13.517%	$191.3556	$191.36	$191.35	$191.40
Purchase #6	$43.75	13.732%	$49.7578	$49.76	$49.75	$49.80
Purchase #7	$179.82	3.330%	$185.808	$185.81	$185.80	$185.80
7 purchase totals =	$1,180.54		$1,286.9783	$1,286.99	$1,287.00	$1,287.10