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	$120.61	3.184%	$124.4502	$124.45	$124.45	$124.50
Purchase #2	$59.46	12.632%	$66.971	$66.97	$66.95	$67.00
Purchase #3	$72.44	8.438%	$78.5525	$78.55	$78.55	$78.60
Purchase #4	$82.32	12.523%	$92.6289	$92.63	$92.65	$92.60
Purchase #5	$193.28	6.297%	$205.4508	$205.45	$205.45	$205.50
Purchase #6	$165.76	8.469%	$179.7982	$179.80	$179.80	$179.80
Purchase #7	$190.92	6.603%	$203.5264	$203.53	$203.55	$203.50
7 purchase totals =	$884.79		$951.3780	$951.38	$951.40	$951.50