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	$120.56	7.863%	$130.0396	$130.04	$130.05	$130.00
Purchase #2	$229.86	3.805%	$238.6062	$238.61	$238.60	$238.60
Purchase #3	$125.80	12.443%	$141.4533	$141.45	$141.45	$141.50
Purchase #4	$194.61	13.214%	$220.3258	$220.33	$220.35	$220.30
Purchase #5	$224.41	3.149%	$231.4767	$231.48	$231.50	$231.50
Purchase #6	$13.42	4.226%	$13.9871	$13.99	$14.00	$14.00
Purchase #7	$127.77	4.791%	$133.8915	$133.89	$133.90	$133.90
7 purchase totals =	$1,036.43		$1,109.7802	$1,109.79	$1,109.85	$1,109.80