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	$164.70	8.734%	$179.0849	$179.08	$179.10	$179.10
Purchase #2	$140.78	13.690%	$160.0528	$160.05	$160.05	$160.10
Purchase #3	$175.38	3.544%	$181.5955	$181.60	$181.60	$181.60
Purchase #4	$128.53	8.524%	$139.4859	$139.49	$139.50	$139.50
Purchase #5	$66.78	7.154%	$71.5574	$71.56	$71.55	$71.60
Purchase #6	$91.45	11.726%	$102.1734	$102.17	$102.15	$102.20
Purchase #7	$134.70	13.860%	$153.3694	$153.37	$153.35	$153.40
7 purchase totals =	$902.32		$987.3193	$987.32	$987.30	$987.50