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	$244.60	4.400%	$255.3624	$255.36	$255.35	$255.40
Purchase #2	$244.26	8.675%	$265.4496	$265.45	$265.45	$265.40
Purchase #3	$139.90	12.620%	$157.5554	$157.56	$157.55	$157.60
Purchase #4	$81.39	9.497%	$89.1196	$89.12	$89.10	$89.10
Purchase #5	$248.96	3.367%	$257.3425	$257.34	$257.35	$257.30
Purchase #6	$181.85	4.850%	$190.6697	$190.67	$190.65	$190.70
Purchase #7	$7.82	10.874%	$8.6703	$8.67	$8.65	$8.70
7 purchase totals =	$1,148.78		$1,224.1695	$1,224.17	$1,224.10	$1,224.20