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	$204.67	3.560%	$211.9563	$211.96	$211.95	$212.00
Purchase #2	$33.63	6.568%	$35.8388	$35.84	$35.85	$35.80
Purchase #3	$136.51	4.665%	$142.8782	$142.88	$142.90	$142.90
Purchase #4	$55.82	11.459%	$62.2164	$62.22	$62.20	$62.20
Purchase #5	$112.74	9.643%	$123.6115	$123.61	$123.60	$123.60
Purchase #6	$156.34	6.328%	$166.2332	$166.23	$166.25	$166.20
Purchase #7	$10.96	5.821%	$11.598	$11.60	$11.60	$11.60
7 purchase totals =	$710.67		$754.3324	$754.34	$754.35	$754.30