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	$57.33	3.747%	$59.4782	$59.48	$59.50	$59.50
Purchase #2	$49.75	11.342%	$55.3926	$55.39	$55.40	$55.40
Purchase #3	$76.79	13.459%	$87.1252	$87.13	$87.15	$87.10
Purchase #4	$179.37	3.508%	$185.6623	$185.66	$185.65	$185.70
Purchase #5	$47.82	11.599%	$53.3666	$53.37	$53.35	$53.40
Purchase #6	$74.65	8.830%	$81.2416	$81.24	$81.25	$81.20
Purchase #7	$201.59	6.389%	$214.4696	$214.47	$214.45	$214.50
7 purchase totals =	$687.30		$736.7361	$736.74	$736.75	$736.80