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	$139.26	9.417%	$152.3741	$152.37	$152.35	$152.40
Purchase #2	$152.52	9.548%	$167.0826	$167.08	$167.10	$167.10
Purchase #3	$246.39	9.854%	$270.6693	$270.67	$270.65	$270.70
Purchase #4	$53.44	10.418%	$59.0074	$59.01	$59.00	$59.00
Purchase #5	$62.86	5.843%	$66.5329	$66.53	$66.55	$66.50
Purchase #6	$46.62	8.561%	$50.6111	$50.61	$50.60	$50.60
Purchase #7	$9.63	7.449%	$10.3473	$10.35	$10.35	$10.30
7 purchase totals =	$710.72		$776.6247	$776.62	$776.60	$776.60