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	$114.91	7.741%	$123.8052	$123.81	$123.80	$123.80
Purchase #2	$47.85	10.561%	$52.9034	$52.90	$52.90	$52.90
Purchase #3	$40.41	6.595%	$43.075	$43.08	$43.10	$43.10
Purchase #4	$55.31	10.728%	$61.2437	$61.24	$61.25	$61.20
Purchase #5	$242.88	8.161%	$262.7014	$262.70	$262.70	$262.70
Purchase #6	$219.82	10.284%	$242.4263	$242.43	$242.45	$242.40
Purchase #7	$199.44	7.810%	$215.0163	$215.02	$215.00	$215.00
7 purchase totals =	$920.62		$1,001.1713	$1,001.18	$1,001.20	$1,001.10