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	$165.70	8.793%	$180.27	$180.27	$180.25	$180.30
Purchase #2	$161.59	3.665%	$167.5123	$167.51	$167.50	$167.50
Purchase #3	$145.27	8.430%	$157.5163	$157.52	$157.50	$157.50
Purchase #4	$231.69	3.720%	$240.3089	$240.31	$240.30	$240.30
Purchase #5	$108.86	13.726%	$123.8021	$123.80	$123.80	$123.80
Purchase #6	$65.92	9.132%	$71.9398	$71.94	$71.95	$71.90
Purchase #7	$237.78	3.693%	$246.5612	$246.56	$246.55	$246.60
7 purchase totals =	$1,116.81		$1,187.9106	$1,187.91	$1,187.85	$1,187.90