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	$225.32	13.759%	$256.3218	$256.32	$256.30	$256.30
Purchase #2	$49.33	13.377%	$55.9289	$55.93	$55.95	$55.90
Purchase #3	$103.56	13.188%	$117.2175	$117.22	$117.20	$117.20
Purchase #4	$58.86	13.199%	$66.6289	$66.63	$66.65	$66.60
Purchase #5	$107.41	12.218%	$120.5334	$120.53	$120.55	$120.50
Purchase #6	$235.61	4.186%	$245.4726	$245.47	$245.45	$245.50
Purchase #7	$198.77	12.359%	$223.336	$223.34	$223.35	$223.30
7 purchase totals =	$978.86		$1,085.4391	$1,085.44	$1,085.45	$1,085.30