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	$182.92	5.817%	$193.5605	$193.56	$193.55	$193.60
Purchase #2	$187.46	4.704%	$196.2781	$196.28	$196.30	$196.30
Purchase #3	$59.80	4.248%	$62.3403	$62.34	$62.35	$62.30
Purchase #4	$11.88	3.484%	$12.2939	$12.29	$12.30	$12.30
Purchase #5	$177.69	11.470%	$198.071	$198.07	$198.05	$198.10
Purchase #6	$109.77	7.423%	$117.9182	$117.92	$117.90	$117.90
Purchase #7	$78.39	6.443%	$83.4407	$83.44	$83.45	$83.40
7 purchase totals =	$807.91		$863.9027	$863.90	$863.90	$863.90