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	$133.87	6.348%	$142.3681	$142.37	$142.35	$142.40
Purchase #2	$112.38	10.234%	$123.881	$123.88	$123.90	$123.90
Purchase #3	$146.29	8.734%	$159.067	$159.07	$159.05	$159.10
Purchase #4	$201.80	12.687%	$227.4024	$227.40	$227.40	$227.40
Purchase #5	$117.95	11.517%	$131.5343	$131.53	$131.55	$131.50
Purchase #6	$179.33	10.600%	$198.339	$198.34	$198.35	$198.30
Purchase #7	$37.88	6.851%	$40.4752	$40.48	$40.50	$40.50
7 purchase totals =	$929.50		$1,023.0670	$1,023.07	$1,023.10	$1,023.10