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	$144.52	10.807%	$160.1383	$160.14	$160.15	$160.10
Purchase #2	$51.56	7.400%	$55.3754	$55.38	$55.40	$55.40
Purchase #3	$137.63	13.529%	$156.25	$156.25	$156.25	$156.30
Purchase #4	$89.75	3.357%	$92.7629	$92.76	$92.75	$92.80
Purchase #5	$213.96	11.186%	$237.8936	$237.89	$237.90	$237.90
Purchase #6	$189.76	11.666%	$211.8974	$211.90	$211.90	$211.90
Purchase #7	$215.39	5.292%	$226.7884	$226.79	$226.80	$226.80
7 purchase totals =	$1,042.57		$1,141.1060	$1,141.11	$1,141.15	$1,141.20