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	$101.75	3.627%	$105.4405	$105.44	$105.45	$105.40
Purchase #2	$189.65	3.751%	$196.7638	$196.76	$196.75	$196.80
Purchase #3	$162.44	9.484%	$177.8458	$177.85	$177.85	$177.80
Purchase #4	$165.47	3.347%	$171.0083	$171.01	$171.00	$171.00
Purchase #5	$241.72	7.193%	$259.1069	$259.11	$259.10	$259.10
Purchase #6	$160.89	13.705%	$182.94	$182.94	$182.95	$182.90
Purchase #7	$109.25	5.144%	$114.8698	$114.87	$114.85	$114.90
7 purchase totals =	$1,131.17		$1,207.9751	$1,207.98	$1,207.95	$1,207.90