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	$244.58	8.112%	$264.4203	$264.42	$264.40	$264.40
Purchase #2	$58.25	5.274%	$61.3221	$61.32	$61.30	$61.30
Purchase #3	$38.75	12.500%	$43.5938	$43.59	$43.60	$43.60
Purchase #4	$150.60	13.200%	$170.4792	$170.48	$170.50	$170.50
Purchase #5	$47.38	13.399%	$53.7284	$53.73	$53.75	$53.70
Purchase #6	$229.48	7.548%	$246.8012	$246.80	$246.80	$246.80
Purchase #7	$211.54	11.314%	$235.4736	$235.47	$235.45	$235.50
7 purchase totals =	$980.58		$1,075.8186	$1,075.81	$1,075.80	$1,075.80