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	$152.68	10.315%	$168.4289	$168.43	$168.45	$168.40
Purchase #2	$140.75	3.227%	$145.292	$145.29	$145.30	$145.30
Purchase #3	$221.78	11.167%	$246.5462	$246.55	$246.55	$246.50
Purchase #4	$33.95	9.724%	$37.2513	$37.25	$37.25	$37.30
Purchase #5	$94.38	7.286%	$101.2565	$101.26	$101.25	$101.30
Purchase #6	$102.88	9.142%	$112.2853	$112.29	$112.30	$112.30
Purchase #7	$36.71	4.211%	$38.2559	$38.26	$38.25	$38.30
7 purchase totals =	$783.13		$849.3161	$849.33	$849.35	$849.40