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	$238.40	6.238%	$253.2714	$253.27	$253.25	$253.30
Purchase #2	$212.78	5.508%	$224.4999	$224.50	$224.50	$224.50
Purchase #3	$162.59	7.110%	$174.1501	$174.15	$174.15	$174.20
Purchase #4	$162.34	10.769%	$179.8224	$179.82	$179.80	$179.80
Purchase #5	$237.48	6.566%	$253.0729	$253.07	$253.05	$253.10
Purchase #6	$193.48	13.474%	$219.5495	$219.55	$219.55	$219.50
Purchase #7	$144.96	5.162%	$152.4428	$152.44	$152.45	$152.40
7 purchase totals =	$1,352.03		$1,456.8090	$1,456.80	$1,456.75	$1,456.80