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	$202.77	7.359%	$217.6918	$217.69	$217.70	$217.70
Purchase #2	$164.27	11.700%	$183.4896	$183.49	$183.50	$183.50
Purchase #3	$64.50	6.215%	$68.5087	$68.51	$68.50	$68.50
Purchase #4	$78.74	11.613%	$87.8841	$87.88	$87.90	$87.90
Purchase #5	$162.72	12.504%	$183.0665	$183.07	$183.05	$183.10
Purchase #6	$134.80	11.596%	$150.4314	$150.43	$150.45	$150.40
Purchase #7	$78.56	4.565%	$82.1463	$82.15	$82.15	$82.10
7 purchase totals =	$886.36		$973.2184	$973.22	$973.25	$973.20