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	$223.52	5.499%	$235.8114	$235.81	$235.80	$235.80
Purchase #2	$87.25	3.734%	$90.5079	$90.51	$90.50	$90.50
Purchase #3	$66.93	6.333%	$71.1687	$71.17	$71.15	$71.20
Purchase #4	$230.64	5.338%	$242.9516	$242.95	$242.95	$243.00
Purchase #5	$81.78	6.106%	$86.7735	$86.77	$86.75	$86.80
Purchase #6	$72.59	3.427%	$75.0777	$75.08	$75.10	$75.10
Purchase #7	$247.45	13.775%	$281.5362	$281.54	$281.55	$281.50
7 purchase totals =	$1,010.16		$1,083.8270	$1,083.83	$1,083.80	$1,083.90