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	$233.77	13.619%	$265.6071	$265.61	$265.60	$265.60
Purchase #2	$232.27	5.298%	$244.5757	$244.58	$244.60	$244.60
Purchase #3	$208.54	4.800%	$218.5499	$218.55	$218.55	$218.50
Purchase #4	$136.80	13.595%	$155.398	$155.40	$155.40	$155.40
Purchase #5	$60.53	3.703%	$62.7714	$62.77	$62.75	$62.80
Purchase #6	$221.46	9.802%	$243.1675	$243.17	$243.15	$243.20
Purchase #7	$162.48	3.110%	$167.5331	$167.53	$167.55	$167.50
7 purchase totals =	$1,255.85		$1,357.6027	$1,357.61	$1,357.60	$1,357.60