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	$139.47	3.627%	$144.5286	$144.53	$144.55	$144.50
Purchase #2	$131.39	9.850%	$144.3319	$144.33	$144.35	$144.30
Purchase #3	$133.37	6.821%	$142.4672	$142.47	$142.45	$142.50
Purchase #4	$163.37	13.281%	$185.0672	$185.07	$185.05	$185.10
Purchase #5	$179.31	5.716%	$189.5594	$189.56	$189.55	$189.60
Purchase #6	$106.32	13.167%	$120.3192	$120.32	$120.30	$120.30
Purchase #7	$144.56	10.862%	$160.2621	$160.26	$160.25	$160.30
7 purchase totals =	$997.79		$1,086.5356	$1,086.54	$1,086.50	$1,086.60