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	$34.25	3.469%	$35.4381	$35.44	$35.45	$35.40
Purchase #2	$59.96	10.721%	$66.3883	$66.39	$66.40	$66.40
Purchase #3	$89.82	8.293%	$97.2688	$97.27	$97.25	$97.30
Purchase #4	$160.37	13.655%	$182.2685	$182.27	$182.25	$182.30
Purchase #5	$77.33	10.161%	$85.1875	$85.19	$85.20	$85.20
Purchase #6	$44.66	7.365%	$47.9492	$47.95	$47.95	$47.90
Purchase #7	$248.46	4.194%	$258.8804	$258.88	$258.90	$258.90
7 purchase totals =	$714.85		$773.3808	$773.39	$773.40	$773.40