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	$210.68	4.853%	$220.9043	$220.90	$220.90	$220.90
Purchase #2	$73.66	9.392%	$80.5781	$80.58	$80.60	$80.60
Purchase #3	$131.94	5.336%	$138.9803	$138.98	$139.00	$139.00
Purchase #4	$184.93	6.437%	$196.8339	$196.83	$196.85	$196.80
Purchase #5	$169.72	12.106%	$190.2663	$190.27	$190.25	$190.30
Purchase #6	$49.89	3.453%	$51.6127	$51.61	$51.60	$51.60
Purchase #7	$181.49	9.512%	$198.7533	$198.75	$198.75	$198.80
7 purchase totals =	$1,002.31		$1,077.9289	$1,077.92	$1,077.95	$1,078.00