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	$214.92	7.760%	$231.5978	$231.60	$231.60	$231.60
Purchase #2	$59.80	5.789%	$63.2618	$63.26	$63.25	$63.30
Purchase #3	$170.85	9.380%	$186.8757	$186.88	$186.90	$186.90
Purchase #4	$195.34	10.275%	$215.4112	$215.41	$215.40	$215.40
Purchase #5	$156.95	6.698%	$167.4625	$167.46	$167.45	$167.50
Purchase #6	$29.33	6.805%	$31.3259	$31.33	$31.35	$31.30
Purchase #7	$18.98	12.113%	$21.279	$21.28	$21.30	$21.30
7 purchase totals =	$846.17		$917.2139	$917.22	$917.25	$917.30