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	$204.32	6.442%	$217.4823	$217.48	$217.50	$217.50
Purchase #2	$199.81	7.807%	$215.4092	$215.41	$215.40	$215.40
Purchase #3	$121.91	4.744%	$127.6934	$127.69	$127.70	$127.70
Purchase #4	$8.89	7.168%	$9.5272	$9.53	$9.55	$9.50
Purchase #5	$235.32	10.168%	$259.2473	$259.25	$259.25	$259.20
Purchase #6	$78.58	4.611%	$82.2033	$82.20	$82.20	$82.20
Purchase #7	$138.84	3.629%	$143.8785	$143.88	$143.90	$143.90
7 purchase totals =	$987.67		$1,055.4412	$1,055.44	$1,055.50	$1,055.40