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	$245.92	10.514%	$271.776	$271.78	$271.80	$271.80
Purchase #2	$157.95	11.846%	$176.6608	$176.66	$176.65	$176.70
Purchase #3	$129.52	7.664%	$139.4464	$139.45	$139.45	$139.40
Purchase #4	$113.98	10.114%	$125.5079	$125.51	$125.50	$125.50
Purchase #5	$70.83	10.804%	$78.4825	$78.48	$78.50	$78.50
Purchase #6	$72.27	7.259%	$77.5161	$77.52	$77.50	$77.50
Purchase #7	$242.63	7.836%	$261.6425	$261.64	$261.65	$261.60
7 purchase totals =	$1,033.10		$1,131.0322	$1,131.04	$1,131.05	$1,131.00