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	$40.61	3.652%	$42.0931	$42.09	$42.10	$42.10
Purchase #2	$53.54	11.257%	$59.567	$59.57	$59.55	$59.60
Purchase #3	$246.54	3.385%	$254.8854	$254.89	$254.90	$254.90
Purchase #4	$126.86	3.208%	$130.9297	$130.93	$130.95	$130.90
Purchase #5	$92.55	12.120%	$103.7671	$103.77	$103.75	$103.80
Purchase #6	$155.50	8.579%	$168.8403	$168.84	$168.85	$168.80
Purchase #7	$227.27	8.632%	$246.8879	$246.89	$246.90	$246.90
7 purchase totals =	$942.87		$1,006.9705	$1,006.98	$1,007.00	$1,007.00