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	$62.69	4.235%	$65.3449	$65.34	$65.35	$65.30
Purchase #2	$213.31	12.753%	$240.5134	$240.51	$240.50	$240.50
Purchase #3	$29.51	3.426%	$30.521	$30.52	$30.50	$30.50
Purchase #4	$228.79	7.138%	$245.121	$245.12	$245.10	$245.10
Purchase #5	$89.57	8.874%	$97.5184	$97.52	$97.50	$97.50
Purchase #6	$110.25	11.843%	$123.3069	$123.31	$123.30	$123.30
Purchase #7	$134.52	7.699%	$144.8767	$144.88	$144.90	$144.90
7 purchase totals =	$868.64		$947.2023	$947.20	$947.15	$947.10