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	$48.86	11.348%	$54.4046	$54.40	$54.40	$54.40
Purchase #2	$243.36	7.611%	$261.8821	$261.88	$261.90	$261.90
Purchase #3	$189.97	6.859%	$203	$203.00	$203.00	$203.00
Purchase #4	$248.99	3.153%	$256.8407	$256.84	$256.85	$256.80
Purchase #5	$65.29	11.144%	$72.5659	$72.57	$72.55	$72.60
Purchase #6	$41.27	12.416%	$46.3941	$46.39	$46.40	$46.40
Purchase #7	$208.85	13.189%	$236.3952	$236.40	$236.40	$236.40
7 purchase totals =	$1,046.59		$1,131.4826	$1,131.48	$1,131.50	$1,131.50