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	$155.27	6.128%	$164.7849	$164.78	$164.80	$164.80
Purchase #2	$65.27	11.656%	$72.8779	$72.88	$72.90	$72.90
Purchase #3	$33.29	5.471%	$35.1113	$35.11	$35.10	$35.10
Purchase #4	$50.49	6.409%	$53.7259	$53.73	$53.75	$53.70
Purchase #5	$119.90	9.558%	$131.36	$131.36	$131.35	$131.40
Purchase #6	$211.72	3.227%	$218.5522	$218.55	$218.55	$218.60
Purchase #7	$63.69	7.697%	$68.5922	$68.59	$68.60	$68.60
7 purchase totals =	$699.63		$745.0044	$745.00	$745.05	$745.10