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	$191.54	12.730%	$215.923	$215.92	$215.90	$215.90
Purchase #2	$134.88	4.221%	$140.5733	$140.57	$140.55	$140.60
Purchase #3	$97.89	12.126%	$109.7601	$109.76	$109.75	$109.80
Purchase #4	$32.94	9.787%	$36.1638	$36.16	$36.15	$36.20
Purchase #5	$210.85	10.802%	$233.626	$233.63	$233.65	$233.60
Purchase #6	$156.61	12.584%	$176.3178	$176.32	$176.30	$176.30
Purchase #7	$139.43	5.229%	$146.7208	$146.72	$146.70	$146.70
7 purchase totals =	$964.14		$1,059.0848	$1,059.08	$1,059.00	$1,059.10