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	$59.88	4.630%	$62.6524	$62.65	$62.65	$62.70
Purchase #2	$84.82	13.822%	$96.5438	$96.54	$96.55	$96.50
Purchase #3	$36.76	5.328%	$38.7186	$38.72	$38.70	$38.70
Purchase #4	$216.25	3.106%	$222.9667	$222.97	$222.95	$223.00
Purchase #5	$5.46	11.547%	$6.0905	$6.09	$6.10	$6.10
Purchase #6	$68.57	5.600%	$72.4099	$72.41	$72.40	$72.40
Purchase #7	$169.68	11.462%	$189.1287	$189.13	$189.15	$189.10
7 purchase totals =	$641.42		$688.5106	$688.51	$688.50	$688.50