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	$91.93	8.215%	$99.482	$99.48	$99.50	$99.50
Purchase #2	$12.78	10.572%	$14.1311	$14.13	$14.15	$14.10
Purchase #3	$230.71	3.397%	$238.5472	$238.55	$238.55	$238.50
Purchase #4	$207.34	8.813%	$225.6129	$225.61	$225.60	$225.60
Purchase #5	$222.59	6.527%	$237.1184	$237.12	$237.10	$237.10
Purchase #6	$80.39	13.766%	$91.4565	$91.46	$91.45	$91.50
Purchase #7	$96.63	6.500%	$102.911	$102.91	$102.90	$102.90
7 purchase totals =	$942.37		$1,009.2591	$1,009.26	$1,009.25	$1,009.20