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	$55.26	7.311%	$59.3001	$59.30	$59.30	$59.30
Purchase #2	$109.55	3.565%	$113.4555	$113.46	$113.45	$113.50
Purchase #3	$50.44	8.481%	$54.7178	$54.72	$54.70	$54.70
Purchase #4	$169.29	12.580%	$190.5867	$190.59	$190.60	$190.60
Purchase #5	$192.67	3.751%	$199.8971	$199.90	$199.90	$199.90
Purchase #6	$186.51	5.780%	$197.2903	$197.29	$197.30	$197.30
Purchase #7	$205.97	9.696%	$225.9409	$225.94	$225.95	$225.90
7 purchase totals =	$969.69		$1,041.1884	$1,041.20	$1,041.20	$1,041.20