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	$167.37	10.622%	$185.148	$185.15	$185.15	$185.10
Purchase #2	$230.81	5.540%	$243.5969	$243.60	$243.60	$243.60
Purchase #3	$24.64	11.272%	$27.4174	$27.42	$27.40	$27.40
Purchase #4	$141.49	12.150%	$158.681	$158.68	$158.70	$158.70
Purchase #5	$88.46	11.317%	$98.471	$98.47	$98.45	$98.50
Purchase #6	$111.26	10.872%	$123.3562	$123.36	$123.35	$123.40
Purchase #7	$117.63	5.356%	$123.9303	$123.93	$123.95	$123.90
7 purchase totals =	$881.66		$960.6008	$960.61	$960.60	$960.60