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	$57.39	6.171%	$60.9315	$60.93	$60.95	$60.90
Purchase #2	$190.38	11.340%	$211.9691	$211.97	$211.95	$212.00
Purchase #3	$115.29	10.625%	$127.5396	$127.54	$127.55	$127.50
Purchase #4	$227.32	12.815%	$256.4511	$256.45	$256.45	$256.50
Purchase #5	$225.76	13.352%	$255.9035	$255.90	$255.90	$255.90
Purchase #6	$84.69	5.535%	$89.3776	$89.38	$89.40	$89.40
Purchase #7	$150.87	8.494%	$163.6849	$163.68	$163.70	$163.70
7 purchase totals =	$1,051.70		$1,165.8573	$1,165.85	$1,165.90	$1,165.90