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	$241.77	9.628%	$265.0476	$265.05	$265.05	$265.00
Purchase #2	$50.91	8.168%	$55.0683	$55.07	$55.05	$55.10
Purchase #3	$55.85	7.627%	$60.1097	$60.11	$60.10	$60.10
Purchase #4	$131.89	11.187%	$146.6445	$146.64	$146.65	$146.60
Purchase #5	$198.33	7.628%	$213.4586	$213.46	$213.45	$213.50
Purchase #6	$62.77	12.380%	$70.5409	$70.54	$70.55	$70.50
Purchase #7	$179.59	10.725%	$198.851	$198.85	$198.85	$198.90
7 purchase totals =	$921.11		$1,009.7206	$1,009.72	$1,009.70	$1,009.70