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	$197.39	12.466%	$221.9966	$222.00	$222.00	$222.00
Purchase #2	$240.60	6.218%	$255.5605	$255.56	$255.55	$255.60
Purchase #3	$42.45	3.357%	$43.875	$43.88	$43.90	$43.90
Purchase #4	$72.36	7.869%	$78.054	$78.05	$78.05	$78.10
Purchase #5	$179.46	4.728%	$187.9449	$187.94	$187.95	$187.90
Purchase #6	$38.81	8.394%	$42.0677	$42.07	$42.05	$42.10
Purchase #7	$215.42	6.748%	$229.9565	$229.96	$229.95	$230.00
7 purchase totals =	$986.49		$1,059.4552	$1,059.46	$1,059.45	$1,059.60