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	$125.39	11.404%	$139.6895	$139.69	$139.70	$139.70
Purchase #2	$135.90	6.498%	$144.7308	$144.73	$144.75	$144.70
Purchase #3	$69.61	4.772%	$72.9318	$72.93	$72.95	$72.90
Purchase #4	$70.35	3.620%	$72.8967	$72.90	$72.90	$72.90
Purchase #5	$135.54	3.765%	$140.6431	$140.64	$140.65	$140.60
Purchase #6	$170.77	9.236%	$186.5423	$186.54	$186.55	$186.50
Purchase #7	$228.31	9.159%	$249.2209	$249.22	$249.20	$249.20
7 purchase totals =	$935.87		$1,006.6551	$1,006.65	$1,006.70	$1,006.50