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	$215.40	4.137%	$224.3111	$224.31	$224.30	$224.30
Purchase #2	$118.80	10.682%	$131.4902	$131.49	$131.50	$131.50
Purchase #3	$181.50	10.410%	$200.3942	$200.39	$200.40	$200.40
Purchase #4	$163.79	3.487%	$169.5014	$169.50	$169.50	$169.50
Purchase #5	$90.43	13.390%	$102.5386	$102.54	$102.55	$102.50
Purchase #6	$159.26	7.645%	$171.4354	$171.44	$171.45	$171.40
Purchase #7	$215.70	5.844%	$228.3055	$228.31	$228.30	$228.30
7 purchase totals =	$1,144.88		$1,227.9764	$1,227.98	$1,228.00	$1,227.90