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	$97.54	4.204%	$101.6406	$101.64	$101.65	$101.60
Purchase #2	$201.49	4.749%	$211.0588	$211.06	$211.05	$211.10
Purchase #3	$81.28	10.549%	$89.8542	$89.85	$89.85	$89.90
Purchase #4	$61.33	4.491%	$64.0843	$64.08	$64.10	$64.10
Purchase #5	$102.73	12.791%	$115.8702	$115.87	$115.85	$115.90
Purchase #6	$56.29	11.626%	$62.8343	$62.83	$62.85	$62.80
Purchase #7	$141.75	9.273%	$154.8945	$154.89	$154.90	$154.90
7 purchase totals =	$742.41		$800.2369	$800.22	$800.25	$800.30