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	$218.42	3.440%	$225.9336	$225.93	$225.95	$225.90
Purchase #2	$9.59	6.590%	$10.222	$10.22	$10.20	$10.20
Purchase #3	$71.29	10.436%	$78.7298	$78.73	$78.75	$78.70
Purchase #4	$67.88	10.633%	$75.0977	$75.10	$75.10	$75.10
Purchase #5	$117.27	13.322%	$132.8927	$132.89	$132.90	$132.90
Purchase #6	$113.54	6.481%	$120.8985	$120.90	$120.90	$120.90
Purchase #7	$132.36	13.849%	$150.6905	$150.69	$150.70	$150.70
7 purchase totals =	$730.35		$794.4648	$794.46	$794.50	$794.40