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	$175.87	11.517%	$196.1249	$196.12	$196.10	$196.10
Purchase #2	$82.44	11.805%	$92.172	$92.17	$92.15	$92.20
Purchase #3	$97.59	12.378%	$109.6697	$109.67	$109.65	$109.70
Purchase #4	$47.70	8.868%	$51.93	$51.93	$51.95	$51.90
Purchase #5	$224.67	10.308%	$247.829	$247.83	$247.85	$247.80
Purchase #6	$239.72	6.568%	$255.4648	$255.46	$255.45	$255.50
Purchase #7	$129.50	10.672%	$143.3202	$143.32	$143.30	$143.30
7 purchase totals =	$997.49		$1,096.5106	$1,096.50	$1,096.45	$1,096.50