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	$197.71	3.348%	$204.3293	$204.33	$204.35	$204.30
Purchase #2	$140.88	6.659%	$150.2612	$150.26	$150.25	$150.30
Purchase #3	$66.89	11.598%	$74.6479	$74.65	$74.65	$74.60
Purchase #4	$215.44	3.681%	$223.3703	$223.37	$223.35	$223.40
Purchase #5	$160.64	12.191%	$180.2236	$180.22	$180.20	$180.20
Purchase #6	$190.93	12.565%	$214.9204	$214.92	$214.90	$214.90
Purchase #7	$109.82	12.519%	$123.5684	$123.57	$123.55	$123.60
7 purchase totals =	$1,082.31		$1,171.3211	$1,171.32	$1,171.25	$1,171.30