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	$205.31	11.511%	$228.9432	$228.94	$228.95	$228.90
Purchase #2	$13.54	5.546%	$14.2909	$14.29	$14.30	$14.30
Purchase #3	$45.57	10.354%	$50.2883	$50.29	$50.30	$50.30
Purchase #4	$141.90	8.197%	$153.5315	$153.53	$153.55	$153.50
Purchase #5	$55.44	12.202%	$62.2048	$62.20	$62.20	$62.20
Purchase #6	$73.89	3.715%	$76.635	$76.64	$76.65	$76.60
Purchase #7	$84.86	6.647%	$90.5006	$90.50	$90.50	$90.50
7 purchase totals =	$620.51		$676.3943	$676.39	$676.45	$676.30