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	$78.51	4.167%	$81.7815	$81.78	$81.80	$81.80
Purchase #2	$179.58	11.648%	$200.4975	$200.50	$200.50	$200.50
Purchase #3	$99.58	12.171%	$111.6999	$111.70	$111.70	$111.70
Purchase #4	$50.95	4.198%	$53.0889	$53.09	$53.10	$53.10
Purchase #5	$57.88	4.116%	$60.2623	$60.26	$60.25	$60.30
Purchase #6	$126.77	8.150%	$137.1018	$137.10	$137.10	$137.10
Purchase #7	$250.72	3.676%	$259.9365	$259.94	$259.95	$259.90
7 purchase totals =	$843.99		$904.3684	$904.37	$904.40	$904.40