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	$48.58	6.143%	$51.5643	$51.56	$51.55	$51.60
Purchase #2	$131.59	6.815%	$140.5579	$140.56	$140.55	$140.60
Purchase #3	$175.45	7.468%	$188.5526	$188.55	$188.55	$188.60
Purchase #4	$201.49	10.424%	$222.4933	$222.49	$222.50	$222.50
Purchase #5	$189.26	3.639%	$196.1472	$196.15	$196.15	$196.10
Purchase #6	$239.76	13.821%	$272.8972	$272.90	$272.90	$272.90
Purchase #7	$227.48	10.548%	$251.4746	$251.47	$251.45	$251.50
7 purchase totals =	$1,213.61		$1,323.6871	$1,323.68	$1,323.65	$1,323.80