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	$63.25	4.201%	$65.9071	$65.91	$65.90	$65.90
Purchase #2	$245.26	6.422%	$261.0106	$261.01	$261.00	$261.00
Purchase #3	$199.48	9.622%	$218.674	$218.67	$218.65	$218.70
Purchase #4	$208.39	4.826%	$218.4469	$218.45	$218.45	$218.40
Purchase #5	$50.99	4.803%	$53.439	$53.44	$53.45	$53.40
Purchase #6	$195.37	11.127%	$217.1088	$217.11	$217.10	$217.10
Purchase #7	$55.30	6.721%	$59.0167	$59.02	$59.00	$59.00
7 purchase totals =	$1,018.04		$1,093.6031	$1,093.61	$1,093.55	$1,093.50