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	$237.47	7.475%	$255.2209	$255.22	$255.20	$255.20
Purchase #2	$165.67	3.379%	$171.268	$171.27	$171.25	$171.30
Purchase #3	$69.82	5.848%	$73.9031	$73.90	$73.90	$73.90
Purchase #4	$40.32	8.750%	$43.848	$43.85	$43.85	$43.80
Purchase #5	$146.90	11.188%	$163.3352	$163.34	$163.35	$163.30
Purchase #6	$155.81	7.391%	$167.3259	$167.33	$167.35	$167.30
Purchase #7	$89.94	7.264%	$96.4732	$96.47	$96.45	$96.50
7 purchase totals =	$905.93		$971.3743	$971.38	$971.35	$971.30