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	$89.41	13.449%	$101.4348	$101.43	$101.45	$101.40
Purchase #2	$203.59	4.255%	$212.2528	$212.25	$212.25	$212.30
Purchase #3	$55.25	10.439%	$61.0175	$61.02	$61.00	$61.00
Purchase #4	$177.60	10.454%	$196.1663	$196.17	$196.15	$196.20
Purchase #5	$109.27	7.738%	$117.7253	$117.73	$117.75	$117.70
Purchase #6	$117.63	13.796%	$133.8582	$133.86	$133.85	$133.90
Purchase #7	$103.34	3.161%	$106.6066	$106.61	$106.60	$106.60
7 purchase totals =	$856.09		$929.0615	$929.07	$929.05	$929.10