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	$126.32	6.682%	$134.7607	$134.76	$134.75	$134.80
Purchase #2	$100.33	11.563%	$111.9312	$111.93	$111.95	$111.90
Purchase #3	$195.65	10.121%	$215.4517	$215.45	$215.45	$215.50
Purchase #4	$233.50	8.636%	$253.6651	$253.67	$253.65	$253.70
Purchase #5	$221.94	11.650%	$247.796	$247.80	$247.80	$247.80
Purchase #6	$87.65	7.544%	$94.2623	$94.26	$94.25	$94.30
Purchase #7	$201.69	10.284%	$222.4318	$222.43	$222.45	$222.40
7 purchase totals =	$1,167.08		$1,280.2988	$1,280.30	$1,280.30	$1,280.40