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	$96.67	4.385%	$100.909	$100.91	$100.90	$100.90
Purchase #2	$159.96	4.626%	$167.3597	$167.36	$167.35	$167.40
Purchase #3	$231.33	3.122%	$238.5521	$238.55	$238.55	$238.60
Purchase #4	$196.96	8.182%	$213.0753	$213.08	$213.10	$213.10
Purchase #5	$28.78	7.823%	$31.0315	$31.03	$31.05	$31.00
Purchase #6	$35.94	5.258%	$37.8297	$37.83	$37.85	$37.80
Purchase #7	$9.86	7.340%	$10.5837	$10.58	$10.60	$10.60
7 purchase totals =	$759.50		$799.3410	$799.34	$799.40	$799.40