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	$158.79	12.627%	$178.8404	$178.84	$178.85	$178.80
Purchase #2	$239.86	6.672%	$255.8635	$255.86	$255.85	$255.90
Purchase #3	$136.72	3.782%	$141.8908	$141.89	$141.90	$141.90
Purchase #4	$179.86	13.177%	$203.5602	$203.56	$203.55	$203.60
Purchase #5	$137.94	5.637%	$145.7157	$145.72	$145.70	$145.70
Purchase #6	$75.91	3.811%	$78.8029	$78.80	$78.80	$78.80
Purchase #7	$182.54	7.676%	$196.5518	$196.55	$196.55	$196.60
7 purchase totals =	$1,111.62		$1,201.2253	$1,201.22	$1,201.20	$1,201.30