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	$32.35	4.735%	$33.8818	$33.88	$33.90	$33.90
Purchase #2	$103.40	5.423%	$109.0074	$109.01	$109.00	$109.00
Purchase #3	$72.56	13.645%	$82.4608	$82.46	$82.45	$82.50
Purchase #4	$198.81	6.106%	$210.9493	$210.95	$210.95	$210.90
Purchase #5	$59.93	6.137%	$63.6079	$63.61	$63.60	$63.60
Purchase #6	$68.77	4.176%	$71.6418	$71.64	$71.65	$71.60
Purchase #7	$74.35	5.317%	$78.3032	$78.30	$78.30	$78.30
7 purchase totals =	$610.17		$649.8522	$649.85	$649.85	$649.80