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	$137.85	4.119%	$143.528	$143.53	$143.55	$143.50
Purchase #2	$136.46	3.256%	$140.9031	$140.90	$140.90	$140.90
Purchase #3	$201.27	5.241%	$211.8186	$211.82	$211.80	$211.80
Purchase #4	$96.93	13.425%	$109.9429	$109.94	$109.95	$109.90
Purchase #5	$90.26	10.561%	$99.7924	$99.79	$99.80	$99.80
Purchase #6	$157.31	9.109%	$171.6394	$171.64	$171.65	$171.60
Purchase #7	$214.38	11.616%	$239.2824	$239.28	$239.30	$239.30
7 purchase totals =	$1,034.46		$1,116.9068	$1,116.90	$1,116.95	$1,116.80