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	$139.87	10.318%	$154.3018	$154.30	$154.30	$154.30
Purchase #2	$112.32	4.407%	$117.2699	$117.27	$117.25	$117.30
Purchase #3	$95.29	13.614%	$108.2628	$108.26	$108.25	$108.30
Purchase #4	$217.50	13.330%	$246.4928	$246.49	$246.50	$246.50
Purchase #5	$90.30	13.350%	$102.3551	$102.36	$102.35	$102.40
Purchase #6	$78.29	5.330%	$82.4629	$82.46	$82.45	$82.50
Purchase #7	$221.57	7.475%	$238.1324	$238.13	$238.15	$238.10
7 purchase totals =	$955.14		$1,049.2777	$1,049.27	$1,049.25	$1,049.40